Western Areas Limited Forrestania Nickel Project Cosmic Boy TSF
Western Areas Limited Forrestania Nickel Project
Cosmic Boy TSF Embankment Raise - Design Report 10 February 2016
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Forrestania Nickel Project
Prepared for Western Areas Limited
Attention: Mr Chris Munro
Prepared by Coffey Mining Pty Ltd Suite 2, 53 Burswood Road Burswood WA 6100 Australia t: +61 8 9269 6200 f: +61 8 9269 6299 ABN: 52 065 481 209
10 February 2016
Document authorisation
Our ref: MINEWPER00345AV-AA
For and on behalf of Coffey
This is a scanned sig nature held on file by Coffey. The person and signatory consents to its use only for the purpose of this document. Christopher Hogg Tailings Manager
Quality information Revision history
Revision Description Date Author Reviewer Signatory A Issued for client review 25/11/2014 FvdL/MG/DL/DN C Hogg C Hogg 0 Issued as Final 22/12/2014 FvdL/MG/DL/DN C Hogg C Hogg 1 Issued as Final 10/02/2016 FvdL/MG/DL/DN C Hogg C Hogg
Distribution
Report Status No. of copies Format Distributed to Date Draft 1 PDF Chris Munro 25/11/2014 Final 3 Hard + CD Chris Munro 22/12/2014 Revised 1 PDF Bryan Williams / Chris Munro 10/02/2016
Coffey Mining Pty Ltd i ABN: 52 065 481 209
Table of contents
Executive Summary ...... i 1. Introduction ...... 1 1.1. Design drawings ...... 2 1.2. Background information ...... 2 1.3. Government conditions ...... 2 1.3.1. Department of Environment Regulation ...... 2 1.3.2. Department of Mines and Petroleum ...... 2 1.4. Tailings parameters ...... 3 1.5. Tailings engineering properties ...... 3 1.6. Previous construction activities ...... 3 2. Proposed staged works ...... 3 2.1. Embankment ...... 3 2.2. Storage capacity ...... 4 2.3. Decant / water recovery ...... 4 2.4. Spigotting ...... 5 3. Construction materials and methods ...... 5 4. Monitoring instrumentation ...... 5 4.1. Monitoring bores ...... 5 4.2. Vibrating wire piezometers ...... 5 5. Seepage assessment ...... 6 5.1. Previous studies ...... 6 5.2. Groundwater monitoring data...... 6 5.3. Numerical modelling ...... 8 5.4. Seepage assessment results ...... 8 5.5. Seepage assessment results discussed ...... 9 5.6. Implementation of the groundwater recovery plan ...... 9 5.7. Seepage analysis for 100 year ARI event ...... 10 5.8. Model assumptions for 100 year ARI event ...... 10 5.9. Seepage analysis results for 100 year ARI event ...... 10 6. Liquefaction assessment ...... 10 7. Stability analysis ...... 11 7.1. Method of analysis ...... 11 7.2. Model descriptions and assumptions ...... 11 7.3. Model assumptions ...... 12 7.4. Results of stability analyses ...... 12
Coffey Mining Pty Ltd ii ABN: 52 065 481 209
8. Deformation analysis ...... 13 8.1. Method of analysis ...... 13 8.2. Model assumptions ...... 13 8.3. Results of deformation analysis ...... 14 9. Surface water management ...... 15 9.1. Internal ...... 15 9.2. External ...... 15 10. Water balance ...... 16 11. Dam break analysis ...... 16 11.1. General ...... 16 11.2. Method of analysis ...... 16 11.3. Dam break calculations ...... 16 11.3.1. Breach characteristics ...... 16 11.3.2. Run-out calculations ...... 17 11.3.3. Results and comments ...... 17 11.4. Dam break consequence ...... 18 11.5. Hazard rating ...... 18 11.6. Controls ...... 19 12. Operations manual ...... 19 13. Rehabilitation and closure ...... 20 14. References ...... 23
Figures
Figure 1 – DMP Freeboard Nomenclature
Tables
Table 1 – Previous construction activities ...... 3 Table 2 – Tailings storage capacity ...... 4 Table 3 – VWP installation details ...... 5 Table 4 – Model parameters - previous analytical/numerical models ...... 6 Table 5 - Modelling scenarios for TSF seepage assessment ...... 8 Table 6 - Model parameters - numerical models ...... 8 Table 7 - Summary of modelling results for northern corridor ...... 8 Table 8 - Summary of modelling results for southern corridor ...... 9 Table 9 - Summary of permeability values - seepage model ...... 10
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Table 10 – Summary of modelling parameters – stability analyses...... 12 Table 11 - Summary of stability analysis results ...... 12 Table 12 - Summary of modelling parameters - deformation analysis ...... 14 Table 13 – Design storage allowance ...... 15 Table 14 – Potential tailings run-out distance – existing TSF dam break (sunny day conditions) ...... 17 Table 15 – Potential tailings run-out distance – TSF southern extension dam break (sunny day scenario) ...... 17 Table 16 – Preliminary closure and rehabilitation monitoring program ...... 22
Appendices
Appendix A - Scope of Works Appendix B - Geotechnical Investigation Report Appendix C - Monitoring Instrumentation Data Appendix D - Seepage Analysis Results Appendix E - Liquefaction Analysis Results Appendix F - Stability Analysis Results Appendix G - Deformation Analysis Results Appendix H - Water Balance Data Appendix I - Dam Break Analyses Appendix J - Preliminary Completion Criteria
Coffey Mining Pty Ltd iv ABN: 52 065 481 209
Forrestania Nickel Project Cosmic Boy TSF Embankment Raise - Design Report
Executive Summary
This document presents tailings storage design details for submission to the Department of Mines and Petroleum (DMP) and the Department of Environmental Regulation (DER), Western Australia (WA), for the development and use of the Cosmic Boy Tailings Storage Facility (TSF) at Western Areas Limited’s (WSA) Forrestania Nickel Project (FNP). FNP is located approximately 80km east of Hyden, WA.
The existing TSF at FNP comprises a single cell, circular in shape. It is proposed that the perimeter embankment of the existing cell be raised by 4m in two stages (Stages 3 and 4), from the current Stage 2 crest level of RL415m to crest level RL419m and that an additional cell, southern extension, be constructed to the south of the existing cell and raised once, to provide tailings storage capacity for approximately an additional 10 years of mine life. The proposed works will provide sufficient storage capacity for approximately 3.6Mt of future tailings production at a deposited dry density of 1.5t/m³. The TSF will occupy a surface area of approximately 54ha.
Subsequent stages on the existing TSF will be constructed from compacted dried tailings, utilising upstream construction techniques. The downstream batters will be protected by an outer zone of mine waste capping. The southern extension starter embankment will be constructed using a combination of mine waste, material borrowed from within the cell footprint area and compacted tailings.
The TSF has been assigned a hazard rating of Medium and is classified as Category 2, based on classification criteria outlined in ANCOLD and the DMP ‘Code of Practice: Tailings Storage Facilities in Western Australia’
Tailings in the form of slurry will be discharged sub-aerially and spirally from the perimeter of each cell. Spigotting will be carried out such that the water ponds are maintained around the decant structure, located in the centre of each cell. The top surface of the deposited tailings will assume the form of a valley sloping toward the decant structures at 1.43% (1in 70). Surface water liberated from the tailings slurry will be recovered via decant pumps deployed within the decant structures. Recovered water will be pumped back to the process plant for reuse.
Allowance for the temporary storage of the 100 year average recurrence interval 72 hour duration storm event has been incorporated into the design of both cells and relies on the correct operation of the facility with respect to freeboard criteria. Critical freeboard criteria are particularly relevant at the end of each filling stage of the TSF, just prior to the next staged embankment lift.
The probability of major embankment failure during the life of the TSF is assessed as being low provided the construction and operation guidelines are adhered to. The procedures described in the existing operating manual are applicable to the raised and extended TSF, however the system description will need updating. Stability analyses for the proposed embankment indicate adequate factors of safety against failure can be achieved under both static and seismic conditions.
The existing monitoring bore network (11 bores) will continue to be used to monitor the performance of the existing TSF. It is recommended that the additional recovery bores, installed in 2011, be commissioned following the stage 3 embankment raising by establishing pumps within the bores. Monitoring of water levels and water quality within the bores is to be completed in accordance with the DER license conditions.
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Forrestania Nickel Project Cosmic Boy TSF Embankment Raise - Design Report
1. Introduction
This report presents a design for staged embankment raising and expansion of the Cosmic Boy Tailings Storage Facility (TSF) at Forrestania Nickel Project (FNP), approximately 80km east of Hyden, Western Australia. The design report was prepared in accordance with the Department of Mines and Petroleum (DMP) (2015)1 ‘Guide to the preparation of a design report for Tailings Storage Facilities (TSFs)’. The existing TSF comprises a paddock-type storage with a centrally located pumped decant. The facility is approximately 300m east of the processing plant and has a current maximum embankment height of 15m above the original ground level.
The works will primarily comprise bulk earthworks to raise the existing perimeter embankment by 4m in two stages (Stages 3 and 4), from the current Stage 2 crest level of RL415m to crest level RL419m. The works will also involve raising the decant access causeway and decant structure by 4m in two stages, from the current crest level of RL413m to crest level RL417m. Southern extension cell works involving starter embankment construction to crest level RL413.5m, with a decant access causeway and decant structure at the same level and a 2.5m embankment raise (Stage 1) to crest level RL416m are included. The current surface area of the TSF is approximately 33ha with a proposed total surface area of approximately 54ha, including the southern extension cell.
The proposed works will provide sufficient storage capacity for approximately 3.6Mt of future tailings production over ten years (to the end of the 2023 financial year).
The TSF has been assigned a hazard rating of Medium and is classified as Category 2, based on classification criteria outlined in ANCOLD (2012)2 and the DMP (2013)3 ‘Code of Practice: Tailings Storage Facilities in Western Australia’. The hazard rating was determined by considering the potential adverse impacts or damage from an embankment failure – refer to Section 11.5 of this report for details. The design, shown on drawings of embankment layouts and cross-sections, is presented in Appendix A.
The design criteria adopted are in accordance with ANCOLD (2012)2.
A Notice of Intent (NOI) for construction of the TSF starter embankment and Stage 1 and 2 embankment raises was compiled by Golder Associates Pty Ltd (Golder) (2005)4. Further background information is provided in Section 1.2.
The following documents are included herein:
Appendix A – Scope of Works Appendix B – Geotechnical Investigation Report Appendix C – Monitoring Instrumentation Data Appendix D – Seepage Analysis results Appendix E – Liquefaction Analysis results Appendix F – Stability Analysis Results Appendix G – Deformation Analysis Results Appendix H – Water Balance Data Appendix I – Dam Break Analyses Appendix J – Preliminary Completion Criteria
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Forrestania Nickel Project Cosmic Boy TSF Embankment Raise - Design Report
1.1. Design drawings
The following drawings (Appendix A) show the current TSF design:
Title Drawing Number General Arrangement Stage 2 MWP00345AV-01 0 General Arrangement Stage 3 MWP00345AV-02 0 General Arrangement extension South MWP00345AV-03 0 Starter embankment General Arrangement Stage 4 MWP00345AV-04 0 General Arrangement extension South MWP00345AV-05 0 Stage 1 embankment Typical Sections – Sheet 1 of 2 MWP00345AV-06 0 Typical Sections – Sheet 2 of 2 MWP00345AV-07 0 Monitoring Bores Locations MWP00345AV-08 0 1.2. Background information
The FNP was previously managed and operated by Outokumpu Mintec Australia Pty Ltd. The original TSF was designed by Soil and Rock Engineering Pty Ltd (SRE) (1992)5, now part of Coffey Mining Pty Ltd (Coffey). The facility was operated from 1992 until closure in 1999. Audits of the original TSF were conducted in 1995, 1997, 1998 and 1999 by SRE. A decommissioning review was conducted in 2000, also by SRE. The original paddock TSF was then rehabilitated by covering the top surface of with a topsoil/waste rock cap. The downstream batters were also rehabilitated.
D.E. Cooper and Associates (DCA) (2004)6 prepared a NOI for construction of a new TSF on top of the existing, rehabilitated TSF. Technical documentation in support of this NOI was produced by Golder (2005)4.
The new TSF, a circular paddock approximately 33ha in footprint area, was constructed on top of the existing TSF in late 2008 / early 2009 under the ownership of Western Areas Limited (WSA), with commissioning in February 2009. Annual audits have been conducted between 2010 and 2014 by Coffey.
The new TSF has previously been raised using the upstream construction method on two occasions (Section 1.6) to a crest RL415m.
The tailings tonnage produced since recommissioning in February 2009 is approximately 1,877,870t. Production rates have been less than the rated throughput of 600,000tpa in the Preamble to the DER Licence (Section 1.3.1.). 1.3. Government conditions
1.3.1. Department of Environment Regulation
The mine is operating under Department of Environment Regulation (DER) Licence No. 8331/2009/2, file number DEC10313, dated 25 January 2012. This licence expires on 26 February 2015.
1.3.2. Department of Mines and Petroleum
The TSF falls under mining lease conditions for Department of Mines and Petroleum (DMP) mining leases M77/335 and M77/399.
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Forrestania Nickel Project Cosmic Boy TSF Embankment Raise - Design Report
1.4. Tailings parameters
According to the Geotechnical Investigation report by Coffey (2014)7 (Appendix B), the following parameters are applicable:
Average slurry density ex-plant 50% solids Final tailings density 1.5t/m³ (dry) Angle of internal friction 38.5º Particle size distribution 44% passing 75 microns (average) Hydraulic Conductivity 10-7m/s to 10-9m/s 1.5. Tailings engineering properties
The following engineering properties are applicable for the tailings (Appendix B):
Plasticity: non-plastic In situ moisture content: approximately 12% (near perimeter embankments) Standard maximum dry density: 2.0t/m³ Optimum moisture content: 13% 1.6. Previous construction activities
The construction history of the TSF is summarised in Table 1, with references to relevant construction documents.
Table 1 – Previous construction activities
Raise height Elevation Design / Stage Date Ref. (m) (RL m) Varies Starter 411.0 February 2009 [8] (3.5m max) Stage 1 2.0 413.0 August 2012 [9] Stage 2 2.0 415.0 July 2014 [10]
2. Proposed staged works 2.1. Embankment
The works will primarily comprise construction of perimeter embankment raises using the upstream construction method, in two stages (Stages 3 and 4) (Drawing No. MWP00345AV-02 and MWP00345AV-04), with construction undertaken on both the existing crest and over the existing tailings beach, using compacted tailings sourced from within the TSF.
Construction of a southern extension starter perimeter embankment, which will be raised by 2.5m (Stage 1) (Drawing No. MWP00345AV-03 and MWP00345AV-05) using the upstream construction method, with construction undertaken on both the existing crest and over the existing tailings beach, using compacted tailings sourced from within the TSF.
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Forrestania Nickel Project Cosmic Boy TSF Embankment Raise - Design Report
The downstream batters will be protected by an outer zone of mine waste capping, sourced from a nominated stockpile on the mine site.
The embankment will have the following geometry:
Downstream batter 1:4 (v:h) Upstream batter 1:1.5 (v:h) Crest width 7.0m Crest crossfall of 2% (sloped inwards into the TSF)
Where construction is undertaken on the existing crest, tyning of the surface followed by watering prior to the placement of the first fill layer will be undertaken. 2.2. Storage capacity
Table 2 presents a summary of the estimated storage characteristics of the TSF for the proposed staged embankment raising. The volume and storage life have been estimated based on a deposited tailings dry density of 1.5t/m³ obtained from laboratory testing, an average tailings beach slope of 1.43% (1 in 70) and advised tailings production over the next ten years of 3.6Mt.
Table 2 – Tailings storage capacity
Tailings Storage Capacity Crest RL Storage Life (mAHD) Volume Tonnage (years) (m3) (t) Stage 2_RL415m 540,000 810,000 1.9 Stage 3_RL417m 520,000 780,000 1.8 SE Starter_RL413.5m 580,000 870,000 1.9 Stage 4_RL419m 495,000 742,500 1.8 Up to end of the 10 year SE Stage 1_RL416m 404,500 606,750 projected period SE = Southern Extension Cell 2.3. Decant / water recovery
Surface water, liberated from the tailings slurry, will be recovered from the TSF via centrally located decant structures. The decant structures will have dedicated pumps to recover and deliver water to the processing plant.
The existing pumped decant centrally located within the TSF consists of vertical concrete rings surrounded by clean rock. The existing decant accessway will be raised along with the perimeter embankments.
A new pumped decant consisting of vertical concrete rings surrounded by clean rock will be installed at the ‘centre’ of the southern extension, located off the southern side of the existing perimeter embankment.
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Forrestania Nickel Project Cosmic Boy TSF Embankment Raise - Design Report
2.4. Spigotting
Tailings placement will be via multi-point spigot discharge. Tailings will be deposited sub-aerially and spirally in a sequential manner around the tailings storage perimeter, in thin layers nominally 300mm thick.
A detailed description of operating procedures is included in an existing Operations Manual11. The procedures described in the existing operating manual are applicable to the raised and extended TSF, however the system description will need updating.
3. Construction materials and methods
A detailed construction and earthworks specification is included in Appendix A, providing a description of construction requirements and procedures for staged embankment raising. Subsequent stages on the existing TSF will be constructed from compacted dried tailings, utilising upstream construction techniques. The downstream batters will be protected by an outer zone of mine waste capping, from a nominated waste dump. The southern extension starter embankment will be constructed using a combination of mine waste, material borrowed from within the cell footprint area and compacted tailings. Refer to Section 2 for a general description of the works.
4. Monitoring instrumentation 4.1. Monitoring bores
A review of the groundwater monitoring information provided by WSA was performed by Coffey. The data is presented in Appendix C. Groundwater is monitored quarterly in eleven bores around the TSF for water level and water quality in accordance with the DER licence condition requirements. A monitoring bore location plan is included in Appendix A (Drawing No. MWP00345AV-08). 4.2. Vibrating wire piezometers
A total of eight Vibrating Wire Piezometers (VWPs) are installed in the TSF. Four are in the perimeter embankment (two north and two south) and four on top of the tailings beach (two north and two south) – Refer to Drawings MWP00345AV-01 to MWP00345AV-05. The VWPs were commissioned at the end of October 2013.
Table 3 – VWP installation details
Probe ID VWP01 VWP02 VWP03 VWP04 VWP05 VWP06 VWP07 VWP08 100D1210 100D1210 100D1217 100D1217 100D1217 100D1217 100D1210 100D1210 Serial Number 74 75 32 29 31 30 73 72 Borehole elevation 413.31 413.19 410 410 410 410 413.03 413.21 (mRL) Borehole depth 15 15.1 9 9.5 VWP sensor tip 14.5 14.6 0.2 0.2 0.2 0.2 8.5 9 (m depth) VWP sensor tip 398.81 398.59 409.8 409.8 409.8 409.8 404.53 404.21 (mRL)
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Forrestania Nickel Project Cosmic Boy TSF Embankment Raise - Design Report
VWP monitoring data is included in Appendix C. It is apparent from interpretation of the data that the phreatic elevation on the northern side of the TSF was at RL403m in July 2014, with the phreatic elevation on the southern side of the TSF at RL404.5m in October 2014.
Additional VWPs (4No, min) will be required in the perimeter embankment for the proposed southern extension. Installation details will be determined on completion of starter embankment construction. 5. Seepage assessment
5.1. Previous studies
Coffey previously conducted two separate seepage assessments for the TSF.
The first study was in 2011, and predicted shallow groundwater mounding beneath and in close proximity to the TSF. A follow-up seepage study, i.e. TSF Groundwater Recovery Plan was undertaken by Coffey (2012)12.
The model parameters used in previous seepage studies are summarised below:
Table 4 – Model parameters - previous analytical/numerical models
Golder Coffey Coffey (2012) (2005)* (2011) Source / Unit layer Porosity Hydraulic conductivity, k Horizontal k Vertical k (m/s) (m/s) (m/s) Tailings 1.0E-07 1.0E-06 1.2E-09 1.0E-05 0.5 Compacted Tailings 1.0E-08 1.0E-08 - - 0.5 Surficial clay 1.0E-07 1.0E-06 1.0E-06 1.0E-06 0.45 Weathered schist 1.0E-06 5.0E-06 1.0E-06 1.0E-06 0.1 Note: (*) Parameters used by Golder (2005) was sighted in Coffey (2011) report.
5.2. Groundwater monitoring data
Historical and recent monitoring data collated from the monitoring and recovery bores are presented on Figure 1.
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Forrestania Nickel Project Cosmic Boy TSF Embankment Raise - Design Report
Figure 1 - Hydrographs for monitoring and recovery bores
The hydrographs indicate pre-2009 water levels were close to steady-state, with the exception of MB08, located on a small spur on the east and up-gradient of the TSF. Significant water level rises after re-commissioning of the TSF were observed around July 2009, in MB01, MB03 and MB06. Water levels also rose in other monitoring bores (North: MB02, MB04, MB05; North-northeast: MB07, MB08; South: MB10, MB11; West: MB09), during subsequent monitoring. These water level rises are the result of localised groundwater mound recharge beneath the TSF, following re-commissioning. Higher seepage rates were observed along the northern side of the TSF, corresponding with higher magnitude water level rises (up to 4m).
Prior to preparation of the TSF groundwater recovery plan in 2012, four recovery bores were installed (in late 2011), all of which were constructed in the vicinity of MB01. Based on the hydrographs (Figure 1), only two (RB01 and RB02) recovery bores were commissioned, mitigating TSF seepage via intermittent pumping. Drawdowns between 7m and 8m occurred, based on the hydrographs. The two active recovery bores up-gradient of MB01 appeared to be quite effective in reducing water level rise in the vicinity of in MB01.
Water levels in MB06 appeared to be unaffected by pumping of both RB01 and RB02. They may increase over time in tandem with rise in tailings level (and associated supernatant water) in the TSF. The water levels measured in MB06 suggest seepage pathways from the TSF towards MB06 are not subject to the drawdown or radius of influence from the current pumping strategy at RB01 and RB02.
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Forrestania Nickel Project Cosmic Boy TSF Embankment Raise - Design Report
5.3. Numerical modelling
Two-dimensional cross-sectional finite element models were developed for groundwater analysis, using Rocscience’s Slide software package.
The models were developed and calibrated to predict groundwater responses following proposed 4m TSF embankment raising, i.e. from the current embankment crest at RL415m (Stage 2) to RL419m (Stage 4). Four models were developed in the assessment, two scenarios each for the northern and southern corridors:
Table 5 - Modelling scenarios for TSF seepage assessment
Base model depicting ‘current’ levels (Stage 2, as of May 2014), CBN_Model1 Northern for calibration and comparison with predictive model. corridor CBN_Model2 Predictive model depicting future TSF perimeter crest levels (Stage 4). Base model depicting ‘current’ levels (Stage 2, as of May 2014), CBS_Model3 Southern for calibration and comparison with predictive model. corridor CBS_Model4 Predictive model depicting future TSF perimeter crest levels (Stage 4).
Calibration for the northern corridor 2-D sections was based on groundwater levels at MB06, and MB10 for the southern corridor 2-D sections, both of which are representative of the water levels for the northern and southern corridor of the current TSF footprint. MB01, which was used as a calibration target in previous seepage studies, was considered unsuitable due to the highly transient nature of water levels, i.e. due to pumping influence from nearby recovery bores. 5.4. Seepage assessment results
Steady-state numerical models for the base cases (CBN_Model1 and CBS_Model3) were adopted for this study and satisfactorily calibrated against the four calibration targets (i.e. two each for the northern and southern corridor), with marginal error noted (between 0.02% and 0.03%). Model parameters adopted for the calibrated numerical models are presented in Table 6. The results of modelling are presented in Tables 7 and 8.
Table 6 - Model parameters - numerical models
Unit layer Hydraulic conductivity (m/s) Tailings 1E-7 Deposited Tailings 1E-8 Surficial clay 1E-7 Weathered schist 2E-7 to 5E-9
Table 7 - Summary of modelling results for northern corridor
Predicted groundwater Predicted depth to Model elevation at MB06 water level at MB06 (mRL) (m bgl) CBN_Model1 396.2 6.4 CBN_Model2 402.2 0.5 Note: bgl – Below ground level
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Table 8 - Summary of modelling results for southern corridor
Predicted groundwater Predicted depth to Model elevation at MB10 water level at MB10 (mRL) (m bgl) CBS_Model3 391.4 18.9 CBS_Model4 39.0 14.3 Note: bgl – Below ground level
2-D sectional modelling results for both the northern and southern corridor sections are presented in Appendix D. The results are discussed in Section 5.5. 5.5. Seepage assessment results discussed
The results from the modelling indicate that a rise of ground water levels due to TSF embankment raising can be expected, to be between 4m (MB10) and 6m (MB06). This implies that future ground water levels will likely exceed the DER limit of 4m below ground level (mbgl) at MB06 (and potentially at MB03, on the northern corridor) should the TSF be raised to the proposed Stage 4 crest height. The predicted depth to groundwater is less than 1m. It is predicted that seepage will occur at the embankment toe along the northern embankment (see results for CBN_Model 2, in Appendix D).
For the southern monitoring bores, M10 and MB11, the predicted groundwater level rise due to TSF raising is not expected to exceed the DER limit of 4mbgl, provided that operational supernatant pond area is managed effectively (pool area be less than 30% of the total TSF surface area). The predicted depth to water at MB10 is approximately 14.3m (i.e. 14.3mbgl).
It must be noted that the models for this study did not take into account the possibility of decreasing tailings permeability over time due to consolidation and heterogeneity in the tailings or subsurface materials. ‘Simplified’ model layers were adopted for the steady-state simulations based on available information. Transient modelling and/or particle tracking simulations (to ascertain seepage pathways and capture zones for recovery bores) can be undertaken if further modelling is required.
Modelling results were found to be sensitive to TSF water levels, hydraulic conductivity of both the tailings and surficial clay, and hydraulic conductivity of the underlying weathered schist. 5.6. Implementation of the groundwater recovery plan
Based on the predicted rise in groundwater levels, it is recommended that the two additional recovery bores installed in 2011, TSF groundwater recovery plan (2012)12, be commissioned following the construction of stage 3 embankment raising, by establishing pumps within the bores. A hydrogeological review may be required at that stage, pending the results of water levels recordings in the monitoring bores.
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Forrestania Nickel Project Cosmic Boy TSF Embankment Raise - Design Report
5.7. Seepage analysis for 100 year ARI event
Seepage analyses were undertaken to estimate the position of the phreatic surface for use in stability modelling and to estimate seepage rates beneath the TSF embankment. A critical section for the final perimeter embankment level of the existing TSF (Northern Cell) and a critical section for the proposed new Southern extension (Southern Cell) were adopted for the analyses. The analyses were carried out using the groundwater module of the GeoStudio 2012 software package ‘Seep/W’. The groundwater module enables two-dimensional finite element analysis to assess groundwater seepage for both saturated and unsaturated steady-state flow conditions. It should be noted that two- dimensional modelling is a simplified approach, which does not take into account three-dimensional effects. 5.8. Model assumptions for 100 year ARI event
Decant pond levels of RL417.35m and RL414.5m were adopted for the analyses. These levels are based on a 1 in 100 year flood event. It was assumed that for a worst case scenario the phreatic surface will reach the ground surface downstream of the TSF. This scenario was considered as the critical condition for embankment stability.
Hydraulic conductivity values adopted for the analyses are summarised in Table 9. The hydraulic conductivity values for the materials were extracted from the TSF Groundwater Recovery Plan (2012)12 and assessed in conjunction with results of a geotechnical assessment by Coffey (2014)7.
Table 9 - Summary of permeability values - seepage model
Hydraulic Conductivity Material K (m/s) Weathered Schist 5.0 x 10-9 Surfacial Clay 1.0 x 10-7 Waste Rock / Topsoil 1.0 x 10-4 Tailings 1.0 x 10-7 Deposited Tailings 1.0 x 10-8 Compacted Tailings 1.0 x 10-8 In-Situ Waste Rock / Topsoil 1.0 x 10-6 Non-Acid Forming Waste 1.0 x 10-7
5.9. Seepage analysis results for 100 year ARI event
The results of the seepage analysis were used in the stability assessment. The phreatic surface, pore pressure contours and seepage flux downstream of the embankment are shown in Appendix D.
6. Liquefaction assessment
A dynamic assessment was undertaken to assess potential for liquefaction following a seismic event. The assessment was undertaken using the GeoLogismiki computer software package, CLiq, based on Robertson (2012)13. The factor of safety was calculated from a ratio of Cyclic Resistance Ratio (CRR) of the soil and Cyclic Stress Ratio (CSR) induced by an earthquake. CRR is the ability of the soil to resist earthquake and CSR is the stress induced by the earthquake in the soil. If the CRR is greater than the CSR (i.e. a factor of safety greater than one) liquefaction is unlikely to occur.
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Forrestania Nickel Project Cosmic Boy TSF Embankment Raise - Design Report
The assessment used raw CPT data with an applied seismic load to analyse the potential for liquefaction. A peak ground acceleration (PGA) of 0.07g, for an Annual Exceedance Probability (AEP) of 1 in 500 was adopted from the Earthquake Hazard Map of Western Australia, i.e. according to Figure 3.2 (C) of AS 1170.4 200714, and a site factor of 2 was applied (i.e. acceleration in analysis was 0.07 x 2 = 0.14g). A conservative earthquake magnitude of 7.0 was adopted. It should be noted that the AEP was in accordance with the requirements of ANCOLD (2012)2 guidelines section 6.
The results indicated there would be minor zones of material which are potentially liquefiable, where the safety factor drops below 1.0. These potential liquefiable zones are between 6m to 10m below the final crest level. It should be noted that for liquefaction to occur there has to be a trigger and the tailings must be saturated. Based on the existence of the aforementioned potential liquefiable zones, a post-liquefaction slope stability analysis was undertaken (refer Section 7). The analysis showed adequate results against factor of safety (Section 7.). Plots of the results of the analyses are in Appendix E.
To avoid potential liquefaction, the TSF should be operated in accordance with the operating manual. The decant pond should be maintained as small as practically possible and kept away from the perimeter embankments.
7. Stability analysis 7.1. Method of analysis
Stability analyses were undertaken to assess the existing TSF embankment raising to crest level RL419m and the proposed southern extension to crest level RL416m. The analyses were undertaken in general accordance with ANCOLD (2012)2.
The GeoStudio 2012 computer package ‘Slope/W’ was used. Slope/W is a two-dimensional stability program used for evaluating factors of safety for circular and non-circular failure surfaces in soil and rock slopes. Slip surfaces were assessed using vertical slice limit equilibrium methods, by the Bishop simplified method. 7.2. Model descriptions and assumptions
The embankment section used in the analyses was based on as-built and design profiles. The tailings strength profile assumed in the models was based on CPTu results for the TSF. A critical section for the Stage 4 perimeter embankment (existing TSF, Northern Cell) and a critical section for the proposed southern extension (Southern Cell) were adopted for the stability analyses. The following scenarios were considered:
Case 1 Perimeter embankment of Northern Cell to crest RL419.0m, raised using upstream construction techniques with compacted tailings. Downstream failure and drained strength (effective stress) parameters under static loading conditions.
Case 2 As in Case 1, with undrained strength (total stress) parameters.
Case 3 As in Case 1 with undrained strength parameters and liquefied shear strengths for liquefiable tailings (post-liquefaction condition).
Case 4 Perimeter embankment of the Southern Cell to crest RL416.0m, constructed using waste rock for the starter embankment and upstream raised using compacted tailings for a single raise. Downstream failure with drained strength parameters and static loading conditions.
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Case 5 As in Case 4, with undrained shear strength parameters. 7.3. Model assumptions
Table 10 provides a summary of strength parameters used in the analyses. The parameters were extracted from geotechnical assessments of the TSF by Coffey (2014)7 and Golder Associates (2005)4. A lower bound liquefied undrained shear strength ratio of 0.04 was adopted from liquefaction assessments for liquefiable tailings. The phreatic surface for cases 1,2,4 and 5 were based on seepage analyses, while for case 4 it was assumed that the water pond is adjacent the perimeter embankment. It is understood that the adopted phreatic surface is conservative.
Table 10 – Summary of modelling parameters – stability analyses
Drained Parameters Undrained Parameters Bulk Density Friction Shear Friction Material Type 3 Cohesion / (kN/m ) / Angle Strength Angle c (kPa) (degrees) Ratio Su/σv (degrees) Weathered Schist 24 100 40 - - Surfacial Clay 15 20 20 - - Waste Rock / Top Soil 20 0 25 - - Tailings 15 0 35 0.5 - Deposited Tailings 15 0 35 0.5 - Compacted Tailings 18 6.5 37 - - In-Situ Waste Rock / Top Soil 20 0 25 - - Non-Acid Forming Waste 20 0 25 - -
7.4. Results of stability analyses
The results of the stability analysis are summarised in Table 11 and the output plots from Slope/W are provided in Appendix F.
Table 11 - Summary of stability analysis results
Recommended Case Location Crest Level Factor of Safety Factor of Safety ANCOLD (2012)8 1 Perimeter Embankment – Northern Cell 419.0m 1.6 1.5 2 Perimeter Embankment – Northern Cell 419.0m 1.3 1.3 3 Perimeter Embankment – Northern Cell 419.0m 1.2 1.0 4 Perimeter Embankment – Southern Cell 416.0m 1.5 1.5 5 Perimeter Embankment – Southern Cell 416.0m 1.5 1.3
The results of the stability analyses indicate the Northern and Southern cells of the TSF at the proposed raised heights have adequate factors of safety against failure under ‘normal’ operating conditions (i.e. decant pond is kept well away from the perimeter embankment). The analyses also confirm that the design geometry for the embankment raise is adequate and the proposed raises (design crest levels of RL419.0m and RL416.0m for Northern and Southern Cell respectively) are achievable.
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The factor of safety against a deep-seated failure through the TSF perimeter embankment is greatly influenced by the position of the phreatic surface. To reduce the risk of failure, the TSF must be operated such that the phreatic surface within the embankment is as low as practical at all times. This can be achieved by maintaining the water pond around the decant facility (e.g. 150m minimum distance away from perimeter embankments), such that no water is allowed to pond against the TSF perimeter embankments. If storm water does extend to the embankment, it will only be a temporary occurrence, as continuous water removal will be undertaken.
8. Deformation analysis 8.1. Method of analysis
ANCOLD (2012)2 indicates that a deformation analysis should be undertaken as part of seismic stability assessment. The analysis allows assessment of damage likely to be caused to the TSF by a design earthquake (i.e. enabling estimation of reduction in freeboard and evaluation of potential for overtopping).
The deformation analysis was undertaken using the dynamic module of the GeoStudio computer package ‘Quake/W’. This program uses a two-dimensional finite element method to determine stress and strain within the embankment under static and dynamic loading conditions. Three different material models, comprising linear elastic, equivalent linear and non-linear, are available for selection in the analysis. The equivalent linear model was adopted in the analysis.
The equivalent linear model is very similar to the linear elastic model. The difference is that the soil stiffness, G, is modified in response to computed strains. Quake/W steps through the entire earthquake record and identifies the peak shear strains at each Gauss numerical integration point in each element. The shear modulus is then modified according to a specified G reduction function, and the process is repeated. This iterative procedure continues until the required G modifications are within a specified tolerance.
The in-situ stress state in the model prior to an earthquake event was established using an initial Quake/W static analysis, which comprised a simple gravity turn-on analysis. The model was subsequently subjected to seismic loading as shown in Figure G1 of Appendix G, with a PGA of 0.07g and duration of 14 seconds. It should be noted that the earthquake applied to the foundation of the TSF and earthquake amplification for the above-ground embankment is taken into account in Quake/W. 8.2. Model assumptions
The model boundary conditions in the deformation analysis were determined based on the rigidity of the foundation against settlement and its flexibility against horizontal movement due to the design earthquake.
It was assumed that there will be no movement at the foundation, as it will be too rigid. It was also assumed that only vertical displacements for the upstream and downstream ends of the model exist. This is where the lateral boundary conditions are set up, to predict the vertical displacements due to the initial gravity stress in the first step of the analysis as described in Section 8.1. In the second step of the analysis, lateral boundary conditions of both ends were set up such that there is free horizontal displacement due to horizontal earthquake loading.
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Table 12 provides a summary of strength parameters used in the analysis. A value of 0.3 for Poisson’s ratio and 0.02 for damping ratio of the materials was assumed, with values for maximum shear modulus (Gmax) adopted based on previous experience with similar materials and textbook values presented in Bowles (1997)15 and Look (2007)16. A lower bound maximum shear modulus of 20Mpa was adopted based on CPT results.
Table 12 - Summary of modelling parameters - deformation analysis
Maximum Friction Cohesion Shear Bulk Density Damping Angle Poisson’s Material c/ Modulus (kN/m3) Ratio / Ratio (kPa) G (degrees) max (MPa) Weathered Schist 24 0.02 100 40 0.3 100 Surfacial Clay 15 0.02 20 20 0.3 30 Waste Rock / Top 20 0.02 0 25 0.3 30 Soil Tailings 15 0.02 0 35 0.3 20 Deposited Tailings 15 0.02 0 35 0.3 20 Compacted Tailings 18 0.02 6.5 37 0.3 50 In-Situ Waste Rock / 20 0.02 0 25 0.3 20 Top Soil Non-Acid Forming 20 0.02 0 25 0.3 20 Waste
8.3. Results of deformation analysis
Figures G2 and G3 show the horizontal acceleration of the Northern Cell and Southern Cell embankment crests during the design earthquake, which is amplified compared with the ground acceleration presented on Figure G1. Figures G4 and G5 show horizontal and vertical displacement contours of the perimeter embankment for the Northern Cell and Figures G6 and G7 show horizontal and vertical displacement contours of the perimeter embankment for the Southern Cell. It should be noted that the scale of deformation displayed on the figures is exaggerated and estimated deformation magnitudes (indicated by contour labels) are shown.
The results indicate the maximum horizontal and vertical displacement will be approximately 26mm and 12mm on the perimeter embankment of Northern Cell. The analyses also show that the approximate peak horizontal and vertical displacements of the perimeter embankment of the Southern Cell will be 20mm and 12mm respectively. The estimated vertical displacements are less than the adopted operational freeboard of 0.3m. Based on the results of the analyses, it is anticipated embankment deformation under seismic loading will be manageable and the operational freeboard will be adequate to prevent loss of tailings by overtopping.
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9. Surface water management 9.1. Internal
The design storage allowance (DSA) of the TSF was estimated using rainfall data obtained from the Australian Government Bureau of Meteorology (BoM). A storm event of 1:100 year Average Recurrence Interval (ARI), 72-hour duration has been considered. Table 13 provides DSA details.
Table 13 – Design storage allowance
Storm Event Precipitation (72-hr rainfall) DSA (m3) 1:100 ARI 150mm 66,326
The TSF catchment area is subject to incident rainfall only, as the facility is a paddock-type storage. The 1:100 year, 72-hour rainfall event equates to 150mm of rainfall. The surface area of the TSF is approximately 442,175m2 (including perimeter embankment crest), thus a total of 66,326m3 of water can be expected to accumulate with a runoff coefficient of 1.0. With rainfall events of this magnitude (i.e. 1:100 year ARI storm event) flooding and disruption to the whole area could be expected.
The TSF has been sized to safely accommodate tailings storage and design rainfall, and the operations manual requires maintenance of adequate operational freeboard (i.e. 300mm). For this reason, the TSF does not have a spillway. DMP freeboard nomenclature is presented as Figure 1.
The PMP (probable maximum precipitation) was calculated in accordance with BoM’s ‘The Estimation of Probable Maximum Precipitation in Australia: Generalised Short-Duration Method.’ BoM (1994)17. The 4-hour PMP rainfall event equates to 590mm of rainfall. The surface area of the TSF is approximately 442,175m2 (including perimeter embankment crest), thus a total of 260,883m3 of water can be expected to accumulate with a runoff coefficient of 1.0. The analyses indicate that with approximately 620,000m3 of storage capacity available in the TSF basin, the ponded water would a minimum of 50m from the closest embankment crest, and the likelihood of the TSF overtopping is considered to be negligible at closure. 9.2. External
Surface water falling on the downstream slope of the TSF will infiltrate into the topsoil and waste rock cover, with the remainder flowing down-slope, as run-off. The perimeter drain will direct flow towards the surface water management pond, located at the western side of the facility, to protect the embankment from damage from surface water flow.
It is estimated that runoff resulting from the 1:100 year ARI storm event and reporting to the surface water management pond will be approximately 15,000m3, assuming a conservatively high runoff coefficient of 30%. This is 50% less than the 30,000m3 of capacity available in the surface water management pond.
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10. Water balance
The TSF water return to the plant is monitored by flow meter. Data provided by WSA (Appendix H) was reviewed by Coffey. The estimated annual average water return as a percentage of slurry water inflow for the period February 2009 to June 2014 was assessed at approximately 32%.
11. Dam break analysis 11.1. General
A dam break analysis, under ‘Sunny day’ conditions, was conducted to assess the extent of tailings flow (or ‘slump’) from a potential TSF embankment breach. The analysis examined a breach of the proposed raised perimeter embankments of both the existing TSF and the southern extension at ultimate design crest elevations of 12m and 9m respectively.
The dam break analysis was performed to assess the consequence of an embankment breach. The assessment considered a breach resulting primarily from overtopping; however, the assessment is also applicable to breaches resulting from liquefaction failure and embankment piping. The peak flows resulting from these secondary events are expected to be lower than compared to those associated with overtopping.
As part of the analysis, a preliminary assessment of population at risk (PAR) was made (Section 11.4). The results of the analysis will be used as a management tool, to develop a site specific TSF Emergency Action Plan. It should be noted that the analysis is a ‘consequence’ assessment, and the results should not be interpreted as indicating the proposed TSF raising presents a likely risk to humans, infrastructure or the environment. 11.2. Method of analysis
The energy-based linear method by Seddon (2010)19, a methodology specifically developed for tailings storages which was presented at the 2011 Mine Waste Conference, was used to assess tailings run-out in the event of embankment failure. The tailings run-out analysis was based on potential energy driving a ‘tailings flow failure’ to the surrounding environment downstream of the TSF, taking into account proposed perimeter embankment elevation.
The volume of tailings likely to be released from the TSF in the event of embankment failure varies depending on the height of embankment at the time of failure and the residual strength of retained materials. For the purposes of the analysis, it was assumed that embankment breaches will be limited to the upstream raised sections of the TSF, and the integrity of the starter embankment which is composed mainly of erosion-resistant mine waste will be maintained. Tailings released from the embankment breaches were assumed to be liquefied and the released tailings volume was estimated based on the tailings storage characteristics of the TSF above starter crest level. 11.3. Dam break calculations
11.3.1. Breach characteristics
It should be noted that tailings is viscous and therefore not as free-flowing when compared to water. If a TSF embankment breach occurs, tailings would only be partially released from the storage impoundment.
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The ‘liquefied’ tailings volumes likely to be released from the existing TSF and the southern extension in the event of an embankment failure under ‘Sunny day’ conditions would be in the order of 0.57Mm³ and 0.09Mm³ respectively (i.e. approximately 30% of the impounded storage volume above starter crest level). This is estimated based on correlations between tailings impoundment and release volumes as derived by Dalpatram (2011)20 relating to a review of data from historic dam failures. Based on MacDonald and Langridge-Monopolis (1984)18, embankment breaches typically occur relatively quickly, over time periods of 0.5 to 4 hours. The calculation of breach characteristics is included in Appendix I.
11.3.2. Run-out calculations
Tailings run-out distances under ‘Sunny day’ conditions were calculated at various values of tailings liquefied shear strength and are summarised in Tables 14 and 15, corresponding to the north-west and south-west movement of released tailings respectively. Calculations of the tailings run-out distances are included in Appendix I.
The released volume was idealised as a rectangular block mass (in accordance with the Seddon method), accounting for the proportion of tailings likely to be released and the geometry of the total tailings mass. The pre-slide configuration adopted for the calculations comprised tailings blocks having breach heights of 12m and 9m, corresponding to proposed raised embankment crest elevations for the existing TSF and the southern extension respectively.
A lower bound liquefied strength ratio of approximately 2% (5% average, 8% upper bound) was determined for the tailings, based on Olsen and Stark (2002) as presented in Fell et al. (2005)21:
Su(LIQ)/σ’vo = 0.03 + 0.0143 (qt) ± 0.03
A lower bound value of cone resistance (qt) of 1.5MPa was adopted based on the results of a CPT investigation carried out by Coffey (2014)7. This value was considered to be conservative.
Table 14 – Potential tailings run-out distance – existing TSF dam break (sunny day conditions)
Undrained Strength Liquefied Shear Tailings Run-Out Tailings Run-out Depth Ratio Strength Distance (m) (m) (%) (kPa) 2% 2.0 310 2.2 5% 5.1 160 3.7 8% 8.2 100 4.9
Table 15 – Potential tailings run-out distance – TSF southern extension dam break (sunny day scenario)
Undrained Strength Liquefied Shear Tailings Run-Out Tailings Run-out Depth Ratio Strength Distance (m) (%) (kPa) (m) 2% 1.5 160 1.0 5% 3.8 90 1.6 8% 6.1 70 2.0
11.3.3. Results and comments
The results give the extent of tailings and ‘operating’ water run-out routing on the downstream side of the TSF in the event of an embankment breach under ‘Sunny day’ conditions.
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It was assumed that there are no downstream detention storage facilities and hence no attenuation of the tailings flow (or ‘slump’) from the dam break. The analysis indicates that a Sunny day ‘slump’ (geotechnical) failure could potential travel 310m and 160m from the TSF, to the north-west and south-west respectively. If the tailings flow were to travel 310m from the TSF, the potential maximum tailings flow depth would be 2.2m above natural ground level.
Based on the results of the analysis, the potential extent of tailings flow is as shown on Figure I1 (Appendix I). It should be noted that the tailings extent shown assumes no additional input from precipitation and no flow downstream in creeks.
The extent of inundation will be greater for PMP or ‘worst’ case conditions. The inundation extent will also be greater if:
A higher percentage of tailings and ‘operating’ water is released (i.e. greater than 30%); Breach characteristics are changed and breach development time is quicker; There is additional contribution to peak flow from the storage facility; and A large rainfall event occurs with a significant volume of water pooling on the facility.
As indicated in Section 11.1, the results of the dam break analysis will be utilised as a management tool to develop a TSF Emergency Action Plan. 11.4. Dam break consequence
The Hazard categorisation of the TSF failure is a function of population at risk (PAR) and estimated severity of damage. The PAR includes all persons who would be directly exposed to the tailings and water stream within the dam break-affected zone if they took no action to evacuate (ANCOLD, 2000)22.
The analysis indicated that if the tailings flow travelled 310m from the TSF site, the potential maximum tailings flow depth would be 2.2m above natural ground level. The plant site is located at RL415m or 7m above natural ground level, so tailings flow resulting from a dam break is considered unlikely to impact the plant site downstream and north-west of the TSF. There would be ample time to move to muster points.
If a TSF dam break were to occur, the tailings and ‘operating’ water would potentially flow to the downstream north-west and south-west areas and have the following impact:
Local mine access roads and tracks to the north, north-west, west and south-west would be affected; Regional access road (Forrestania Southern Cross) to the north-west would be affected; and Contamination of soils would occur, requiring environmental ‘clean-up’.
Based on the dam break consequences described above, the PAR is expected to be low ( <10, including road users). 11.5. Hazard rating
The hazard rating for a TSF was assessed based on the potential consequence of embankment failure. The risk of failure was assessed based on probability and consequence magnitude.
The TSF was assigned a hazard rating of Medium, Category 2, based on classification criteria outlined by the DMP (2013)3. The derivation is outlined below.
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The hazard rating was determined by considering the potential adverse impacts or damage from an embankment failure. The TSF hazard rating was based on the following:
Loss of human life expected (potential loss of life of road users on the local mine access roads and the regional road (Forrestania - Southern Cross) downstream and about 300m west of TSF. PAR estimated at <10. Economic loss due to plant shutdown and production loss, repairs of damaged sections of TSF, local mine access roads and regional road. Environmental impact is expected. Potential for contamination of soils and surface water requiring environmental ‘clean-up’.
Progressing from a hazard rating of ‘Medium’, the TSF category was determined from embankment height using Table 2 of the DMP Code of Practice (2013)3.
The proposed embankment height following 4m raising above the current crest level of RL415m will be 12m, which is less than 15m and therefore the TSF classifies as Category 2. 11.6. Controls
The conditions that need to be present for TSF embankment failure will largely be driven by the size and extent of the decant pond on the facility as well as the magnitude of a trigger seismic event, tailings deformation, the grading of the tailings and the saturation of the tailings adjacent to the embankment. Effective management of the decant pond to ensure excess water is continually removed and the location of the pond is maintained around the decant tower will minimise the risk of a perimeter embankment breach and release of saturated tailings.
TSF embankment failure is not expected provided the facility is operated in accordance with the requirements set out in the Operations Manual11.
Where the TSF is imminent danger of failure and breach, an Emergency Action Plan (EAP) will need to be enacted. This may include closure of local access roads and shutdown of the plant. Trigger events include:
Total Freeboard less than design. Elevated piezometer readings. (i.e. greater than prescribed trigger levels) Significant embankment distress (i.e. significant cracking and slumping). Imminent overtopping of embankment crest.
A geotechnical engineering specialist may need to be consulted prior to enacting the EAP.
12. Operations manual
It is proposed that the existing Operations Manual11 for the TSF be reviewed and updated for the operations of future raises and extensions. The current manual provides a description of the operating procedures, inspection criteria and monitoring requirements for the TSF.
Tailings will be deposited sub-aerially and spirally (in a sequential manner around the tailings storage perimeter) in thin layers via multi-point spigot discharges, so as to develop sloped tailings beaches that concentrate water in the centre of the facility, well away from the perimeter embankments.
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The Emergency Action Plan will be updated as part of the revised Operations Manual. The plan for the plant site should be updated based on the results of the dam break analysis presented in Section 11. The plan should be updated to include management of a TSF dam break.
The plan should include:
Management responsibilities and emergency coordination. Muster points. Seeking of specialist geotechnical advice. Emergency Plan Triggers:
Total Freeboard less than design.
Elevated piezometer readings. (i.e. greater than prescribed trigger levels)
Significant embankment distress (i.e. significant cracking and slumping).
Imminent overtopping of embankment crest.
13. Rehabilitation and closure
The final landform, following two embankment raises to RL419m, will be a maximum of 13m higher than the surrounding TSF. A TSF cover constructed of inert waste material shall be placed on the top surface of the TSF.
The overall design of the TSF cover is to meet the key design objectives, namely: To protect the tailings and provide long term stability; To manage the Probably Maximum Precipitation/Probable Maximum Flood (PMP/PMF); To minimise water ingress to the tailings; and Minimise the risk of acid drainage occurring.
The thickness of the cover material will be further refined closer to closure and in future revisions of the MCP (due in 2016) based the outcomes of detailed tailings and waste characterisation, in order to meet the TSF cover design objectives.
The TSF will have the following features that will make it suitable for long–term stability (both physically and geochemically):
Inert waste material is placed progressively on the downstream slope of the perimeter embankment. This will promote vegetation growth and flatten the slope. The crest will be re-contoured to produce a more rounded surface. Rock armouring of this area will be required to prevent erosion. Access roads, pipework and the decant structure will be decommissioned and compacted areas deep-ripped. The top surface of the TSF (tailings beach) will be left dished and covered with inert overburden waste material, nominally 500mm thick. Topsoil (nominally 200mm thick), will be placed over the waste material. These materials will promote vegetation growth and retard the ingress of water and oxygen into the underlying tailings material and therefore reduce Acid Mine Drainage (AMD) potential. Ponded water in the centre of each cell should evaporate readily, given the high rates of evaporation in the region.
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The top surface of the original TSF will remain covered with the existing cover material (waste rock and topsoil). The perimeter toe drain and associated surface water collection pond will remain in use to drain excess runoff from the downstream face of the TSF.
A re-vegetation plan will form part of the overall rehabilitation plan for the site.
Appendix J outlines the draft Completion Criteria as currently specified in the current Mine Closure Plan 2013. To ensure closure activities are undertaken in accordance with agreed closure objectives, criteria and implementation, closure performance monitoring throughout progressive rehabilitation and post- closure is required.
As specified in the current Mine Closure Plan, post-closure monitoring of revegetation and erosion will be undertaken 2–4 times a year, with more intensive monitoring at the start of the program becoming less intensive as information needs are gradually rationalised. Closure monitoring is expected to continue for up to 10 years following mine closure; when relinquishment of tenements is successfully approved.
Rehabilitation monitoring forms the major component of the Annual Environmental Report (AER) required to be submitted to the DMP each year of operations through to post-closure. The primary function of the AER is to document progress against agreed completion criteria and rehabilitation targets.
A preliminary strategy for monitoring and maintenance has been developed and will be further refined through revisions of the Mine Closure Plan and based on consultation with key stakeholders.
Table 16 outlines the relevant sections of this strategy. WSA has some concerns over the proposed frequency of monitoring and this will be reviewed and updated in the next review and update of the Mine Closure Plan scheduled for September 2016.
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Table 16 – Preliminary closure and rehabilitation monitoring program
Category Actions Purpose Frequency Location Tailings storage Monitor groundwater for To provide data on whether Quarterly Cosmic Boy facility seepage seepage is occurring the RSF Monitor for erosion To provide data on erosion Quarterly Cosmic Boy
Monitor rehabilitation status To provide data on Quarterly Cosmic Boy rehabilitation Surface drainage Monitor surface drainage To provide data on surface Quarterly Across site pathways for erosion and drainage pathways where required sedimentation Monitor surface water To provide data on surface Quarterly Across the site characteristics for potential water geochemistry where required contamination Groundwater Monitor groundwater wells for To provide data on Quarterly Across site potential contamination groundwater geochemistry where required Inspection and Monitor for environmental To provide environmental data Quarterly Across site Monitoring parameters as per program (including water levels, water where required established during assessment quality, soil quality and process (water levels, vegetation growth) across the groundwater and surface water site quality, soil quality, rehabilitation) Update environmental To store environmental data in Quarterly Across site monitoring data register a central repository and ensure where required it is up to date
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14. References
The following provides a summary of standards, references and reports used in this design report.
1. Department of Mines and Petroleum (DMP) (2015). “Guide to the preparation of a design report for Tailings Storage Facilities (TSFs)”. 2. ANCOLD (2012). “Guidelines on Tailings Dam Design, Construction and Operation”. 3. Department of Mines and Petroleum (DMP) (2013). “Code of Practice, Tailings Storage Facilities in Western Australia”. 4. Golder Associates (2005). Technical documentation in support of Notice of Intent for Cosmic Boy Tailings Storage Facility. Reference 05641293-R03, December 2005. 5. Soil & Rock Engineering Pty Ltd (1992). Forrestania Nickel Project, Tailings Dam report to support existing works approval. Reference 3069/00/IG/st, 22 October 1992. 6. D.E. Cooper & Associates Pty Ltd (2004). Forrestania Nickel Operations, Tailings Management New Storage, Notice of Intent. Reference 131-03, December 2004. 7. Coffey Mining (2014). Forrestania Nickel Project, Cosmic Boy Tailings Storage Facility Geotechnical Investigation. Reference MWP00345AV-AB, 22 December 2014. 8. Coffey Mining (2009). Cosmic Boy TSF, Construction Report, Forrestania Nickel Project, Reference MWP00345AF-AD con rep. 9. Coffey Mining (2012) Forrestania Nickel Project, Stage 1 Embankment Raising by 2m to RL413m, Cosmic Boy TSF. Reference MWP00345AL-AB dated 1 August 2012. 10. Coffey Mining (2014) Forrestania Nickel Project, Stage 2 Embankment Raising by 2m to RL415m, Cosmic Boy TSF. Reference MWP00345AS dated 3 July 2014. 11. Western Areas Ltd. Forrestania Nickel Project, Cosmic Boy Tailings Dam Operating Manual. 12. Coffey Mining (2011). TSF Groundwater Recovery Plan for Western Areas NL, Cosmic Boy Project. Reference MINEWPER00345AM-BA, Final report dated 24 February 2012. 13. Robertson, P.K. & Cabal (Robertson), K.L. (2012). Guide to Cone Penetration Testing for Geotechnical Engineering. 14. AS1170.4-2007. Australian Standard Structural design Actions Part 4: Earthquake actions in Australia. 15. Bowles, J.E. (1997). Foundation Analysis and Design, Fifth Edition. McGraw–Hill International Editions. 16. Look, B. (2007). Handbook of Geotechnical Investigation and Design Tables. Taylor & Francis Group, London. 17. Bureau of Meteorology (BoM) (1994). “The Estimation of Probable Maximum Precipitation in Australia: Generalised Short-Duration Method”. 18. T MacDonald and J Langridge - Monopolis (1984). ‘Breaching Characteristics of Dam Failures’, Journal of Hydraulic Engineering, May 1984. 19. Seddon, K. D. (2010). ‘Approaches to run-out distances for liquefied tailings.’ Mine Waste 2010, pp 63-70. 20. A Dalpatram (2011), ‘Estimation of Tailings Dam Break Discharges’, presentation at USSD workshop on Dam Break Analysis Applied to Tailings Dams. 21. Fell, MacGregor & Stapledon (2005). ‘Geotechnical engineering of dams’. 22. ANCOLD (2000). ‘Guidelines on Assessment of the Consequences of Dam Failure’.
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Figures
OPERATIONAL FREEBOARD 300mm MINIMUM POND LEVEL AFTER 1:100 YEAR 72hr RAINFALL EVENT TOTAL FREEBOARD 500mm MINIMUM (DECANT NOT OPERATIONAL) EMBANKMENT CREST NORMAL OPERATING POND LEVEL BEACH FREEBOARD DECANT TOWER
TAILINGS NATURAL GROUND LEVEL
NOTE: FOR CASE WHERE POND IS NORMALLY LOCATED AWAY FROM ANY PERIMETER EMBANKMENTS
REF: DWG: F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Figures\MWP00345AV-Figure_1.dwg Client: Drawn: FvdL WESTERN AREAS LTD Project: Approved: CH COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date: 10/11/2014 Title: Scale: N.T.S. FREEBOARD NOMENCLATURE FROM DMP Project no: Fig no: Rev: Original size: A4 MWP00345AV FIGURE 1 0
Appendix A - Scope of Works
Western Areas Limited Forrestania Nickel Project
Cosmic Boy TSF Embankment Raising - Scope of Works 9 February 2016
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Forrestania Nickel Project
Prepared for Western Areas Limited
Attention: Mr Chris Munro
Prepared by Coffey Mining Pty Ltd Suite 2, 53 Burswood Road, Burswood WA 6100 Australia t: +61 8 9269 6200 f: +61 8 9269 6299 ABN: 52 065 481 209
9 February 2016
Document authorisation
Our ref: MINEWPER00345AV
For and on behalf of Coffey
This is a scanned signature held on file by Coffey. The person andM signatory consents to its use only for the purpose of this document. Greg Ralls Associate Civil / Geotechnical Engineer
Quality information Revision history
Revision Description Date Author Reviewer Signatory A Issued for client review 05/11/2014 Fanie van de G Ralls G Ralls Linde 0 Issued as final 22/12/2014 Fanie van der G Ralls G Ralls Linde 1 Issued as final 09/02/2016 Fanie van der G Ralls G Ralls Linde
Distribution
Report Status No. of copies Format Distributed to Date DRAFT 1 PDF Chris Munro 05/11/2014 FINAL 3 Hard + CD Chris Munro 22/12/2014 REVISED 1 PDF Chris Munro 09/02/2016
Coffey Mining Pty Ltd i ABN: 52 065 481 209
Table of contents
1. Introduction ...... 1 1.1. Contract drawings ...... 1 1.2. Code of practice ...... 1 1.3. Site inspection ...... 2 1.4. Safety ...... 2 1.5. Site location and description ...... 3 2. Description of work ...... 3 2.1. General ...... 3 2.2. Survey ...... 4 2.3. Foundation preparation ...... 4 2.4. Construction materials ...... 5 2.5. Earthworks ...... 5 2.6. Decant Structure ...... 6 2.7. Pipework, Electrical and Instrumentation ...... 7 2.8. Completion ...... 7 3. Construction sequence ...... 7 4. Inspection and testing ...... 8 4.1. Inspection requirements ...... 8 4.2. Testing plans ...... 8 5. Permits, licences and approvals ...... 9 6. Substitutions ...... 9 7. Principal clarification ...... 9 7.1. Communications ...... 10 7.2. Accommodation ...... 10 7.3. Diesel fuel ...... 10 7.4. Flights ...... 10 7.5. Materials ...... 10 7.6. Water ...... 10 7.7. Survey ...... 10 8. Construction information ...... 10 9. Estimate of quantities ...... 11 10. Definition of terms ...... 11
Coffey Mining Pty Ltd i ABN: 52 065 481 209
Tables
Table 1 - Compliance Testing Failure Remedial Action ...... 8 Table 2 - Required Testing Frequency ...... 9
Appendices
Appendix A - Drawings Appendix B - Schedule of Quantities
Coffey Mining Pty Ltd ii ABN: 52 065 481 209
Cosmic Boy TSF Embankment Raising - Scope of Works
1. Introduction
This Scope of Work covers staged construction of the Cosmic Boy Tailings Storage Facility (TSF), located at Forrestania Nickel Mine, and is to be read in conjunction with the construction drawings. The works primarily comprise bulk earthworks to raise the existing perimeter embankment by 4m in two stages (Stages 3 and 4), from the current Stage 2 crest level of RL415m to crest level RL419m. The works also involve the raising of the decant access causeway and decant structure by 4m in two stages, from the current crest level of RL413m to crest level RL417m. Southern extension works involving starter embankment construction to crest level RL413.5m with a decant access causeway and decant structure at the same level, including the construction of a surface water diversion channel along toe of the perimeter embankment. A 2.5m embankment raise (Stage 1) to crest level RL416m, is included.
The Scope of Work shall comprise the provision of all material, construction plant, equipment, labour, supervision, tools, services, warehousing if required, testing equipment, and each and every item necessary for the construction, testing and documentation of the work shown in the drawings, schedules and specifications which form part of the Contract.
All works shall be constructed, completed and operational except as specifically excluded and shall include all necessary auxiliary works, accessories and the incorporation of all miscellaneous material, minor parts and other such items, whether or not the items are specified, where it is clearly the intent of the Contract that they should be supplied or where they are obviously required and necessary to complete and commission the work.
Tailings will be discharged into the TSF being raised. Pipework is controlled and operated by the Principal. The Contractor shall fully co-operate with the pipe handling / operating crew and shall work in with their activities at all times. The Contractor shall protect all active and non-active pipework, electrical cables to decant pumps, pumps and piezometers, which are in place. The Principal shall be immediately notified of any damage to pipework, electrics, pumps or piezometers, no matter how minor. 1.1. Contract drawings
The following drawings are included in Appendix A:
Title Drawing Number General Arrangement Stage 2 MWP00345AV-01 1 General Arrangement Stage 3 MWP00345AV-02 1 General Arrangement extension South MWP00345AV-03 1 Starter embankment General Arrangement Stage 4 MWP00345AV-04 1 General Arrangement extension South MWP00345AV-05 1 Stage 1 embankment Typical Sections – Sheet 1 of 2 MWP00345AV-06 0 Typical Sections – Sheet 2 of 2 MWP00345AV-07 0 Monitoring Bore locations MWP00345AV-08 0 1.2. Code of practice
Unless otherwise specified, or shown on the drawings, the Contractor is to provide all materials and carry out the work in accordance with the latest revisions of the relevant Australian Standard Codes.
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All work under this Contract shall be performed strictly in accordance with the following specifications, drawings and other documents, which by this reference forms part of this Contract, unless expressly noted otherwise.
AS 2124 General conditions of contract.
AS 1289 Methods of testing soils for engineering purposes.
AS 1726 Geotechnical site investigations.
AS 3798 Guidelines on earthworks for commercial and residential developments.
The Works shall be carried out to comply with the latest revision of the Drawings, Codes and Standards specified, or where no standards are specified, to Australian Standards, or to the appropriate British or other recognised Standards.
Before making any change in any work under the Contract to comply with any revisions to the relevant codes and standards, the Contractor shall give to the Principal written notice specifying the reason therefore and requesting their direction thereon. The Principal shall decide whether a change is necessary and issue a variation order accordingly under the provisions of the General Conditions of Contract. 1.3. Site inspection
The Contractor shall inspect the site and must allow for the following factors in their price:
1. The nature and requirements of the work to be done; 2. All conditions on and adjacent to the site; 3. Access to the site; 4. Access roads, available haul roads, traffic restrictions; 5. Traffic management and control; 6. All pipe work; 7. The source of water for construction purposes; 8. The sources of suitable fill material which complies with this Specification; 9. Borrow management, development and restrictions; 10. Material placement requirements; 11. Compliance and material testing requirements; and 12. Prevailing climatic conditions for the site. 1.4. Safety
The Contractor shall:
1. Carry out the works in a safe manner and comply with all of the Principal’s procedures and guidelines. 2. Conform to all relevant Acts or Statutes of Parliament, Regulations, By-Laws or Orders relating to the safety of persons and property on or about the site. 3. All site personnel shall attend a General Site Induction prior to commencing any work on site.
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4. Ensure all site personnel carry out a witnessed breathalyser test daily, and before starting the shift. 1.5. Site location and description
The site is approximately 80km east of Hyden, Western Australia. The TSF comprises a paddock-type storage facility with a centrally located decant structure incorporating a decant pump for water return to the plant. The top surface of the TSF is approximately 30ha in total area.
Tailings deposition will be rotated around the perimeter embankment in a regular manner. The mine is currently operational and, as such, it will be necessary to discharge tailings slurry into the storage while construction is in progress. Tailings distribution pipelines will be managed by Western Areas Ltd prior to, during and upon completion of construction of each stage. To facilitate this work, the Contractor is to provide a plan/programme of the sequence in which the embankment raising will be carried out.
2. Description of work
The earthworks entail:
Construction of perimeter embankment raises using the upstream construction method, in two stages (Stages 3 and 4) (Drawing No. MWP00345AV-02 and MWP00345AV-04), with construction undertaken on both the existing crest and over the existing tailings beach using compacted tailings material sourced from within the TSF. Construction of a southern extension starter perimeter embankment, which will be raised by 2.5m (Stage 1) (Drawing No. MWP00345AV-03 and MWP00345AV-05) using the upstream construction method, with construction undertaken on both the existing crest and over the existing tailings beach using compacted tailings material sourced from within the TSF. Decant accessways, which will be raised along with the perimeter embankments. Installation of concrete decant liner sections. Placement of clean rock around decant structures. Construction of a surface water diversion channel (v-shaped) along toe of the southern extension perimeter embankment to allow flow towards the surface water management pond.
The Scope of Work shall include, but is not necessarily limited to the sections that follow. 2.1. General
The Contractor shall:
Attend a Site Induction before the commencement of works if personnel have not attended a Site Induction in the last three (3) months at the site. Carry out all works indicated or implied on the Drawings and in the Specifications. Supply all labour, plant and materials (except those indicated as being supplied by the Principal) necessary for completion of the works. Maintain all works as required by the Contract documents and for the period stated therein.
All construction shall be to the minimum lines and grades shown on the drawings or as required by the Owner’s Representative as work progresses.
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During the progress of the works, the Owner’s Representative may find it necessary to revise the lines, levels and grades of any part of the works because of the conditions revealed by the works.
The Contractor shall accept reasonable delays due to inspection and checking of any part of the works to determine grades and levels. 2.2. Survey
The Principal will provide bench marks and set out coordinates for the works. The Contractor shall be solely responsible for the setting out of all of the works. The Contractor shall advise the Principal in writing of any discrepancies between the contour information presented on the drawings and ground level survey information obtained by the Contractor.
The embankments shall be constructed to the lines, grades, dimensions and details shown on the Drawings. The tailings beach shall be surveyed prior to the placement of any fill materials. Finished work shall comply with the following tolerances:
The maximum permissible horizontal deviation from the finished lines or zone boundaries shall be -0m to +0.5m. Vertical deviation shall be -0m to +0.2m, provided no abrupt changes in slope or level are present on any finished surface.
The Contractor’s attention is drawn to the possibility of low shear strength materials being encountered on the tailings beach. No payment shall be made for settlement of materials into the tailings beach.
Measurement for payment of all embankment fill material shall be made for the compacted material, measured in place and only to the lines and grades required (excluding tolerances). The Principal may inspect or check any setting out or measurements at any time and the Contractor shall allow for delays while any works are checked.
At the completion of the works the Contractor shall provide detailed as built details, including a hard copy plan layout and survey information in electronic format as well a concise summary of item volumes. 2.3. Foundation preparation
The Contractor shall, as appropriate:
Inspect the embankment crest for any erosion or gullying. Prepare any areas by removing any abrupt grade changes to provide a regular surface for fill placement. Survey or peg the areas so they can be relocated if foundation preparation covers the area with loose material, so it can be removed. All embankment crest areas affected by embankment raising shall be cleared of all gravel and wearing course materials. Where possible recovered gravel material shall be stockpiled for reuse. All embankment crest areas affected by embankment raising shall be cleared of unsuitable materials such as spilled tailings and bull dust, which can be disposed of within the tailings storage area provided it does not obstruct or is located within the footprint of the embankment raising works. The exposed embankment crest surface shall be reviewed and approved by the Owner’s Representative, then scarified (tyned) and thoroughly moisture conditioned. A 150mm thick first lift shall then be placed and machine compacted.
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Tailings beach areas within the embankment footprint forming part of the foundation for the raise shall be scarified to a depth of 300mm in order to remove any visible desiccation cracks, moisture conditioned and machine compacted. Allow for keeping water from excavations by pumping, dewatering, or other suitable means, and adequately dispose of it clear of the works. 2.4. Construction materials
The Contractor shall:
Inspect the construction borrow pit or waste stockpile with the Principal. Agree with the Principal the location and number of any new access ramps at the waste stockpile and at the TSF embankment in order to provide access to the work area. Inspect the waste stockpile and agree with the Principal on the location and levels of benches to allow the safe winning of construction materials. Whilst winning construction materials remove any deleterious materials from the stockpile that may affect either embankment construction or equipment. This will include but not be restricted to oversize rock, tramp steel, cable bolts, wire, and tyres. 2.5. Earthworks
The Contractor shall: Prepare a method statement for the construction of the embankment on the tailings beach. The Contractor’s attention is drawn to the possibility of low shear strength materials being encountered on the tailings beach. The method statement prepared by the Contractor shall not only include details on the proposed method of construction on the tailings beach but also the safety measures to be adopted to ensure the work is carried out with minimal risk to personnel and equipment. The Contractor shall submit details of the proposed method of work on the tailings beach to the Owner’s Representative prior to the commencement of construction. Raise the perimeter embankment of the tailings storage using tailings material sourced from within the TSF. All tailings borrow excavations shall be extended as far as possible away from the perimeter embankment to prevent the excavation of deep trenches immediately adjacent to the embankment. The depth of excavation shall not exceed 1.5m below the existing tailings beach level. The materials borrowed from within the upper 1.5m of the profile in the storage area shall be well mixed to ensure uniform distribution of fines (material less than 75 microns) and moisture. The Contractor shall leave raised bunds in the borrow area at centres of not less than 150m along the embankment perimeter. The bunds shall be of sufficient dimensions to prevent the flow of tailings into the adjacent excavation by collapse of the bund or overtopping. Upon completion of excavation from a section of the borrow area, prior to re-deposition of tailings, finger trenches (1.5m wide) shall be excavated from the borrow area down the tailings beach midway between each bund. The Contractor shall leave a 5m berm, no dig zone, from the upstream toe of the raised embankments. Adjust the moisture content of the borrow material approved for use in the perimeter embankment construction. Moisture condition the borrow to within the range of -2% to +2% of the optimum moisture content (OMC) as determined from Laboratory Test 5.1.1 of AS1289 (2003). The borrow material shall be cured to ensure the moisture is thoroughly mixed and evenly spread through all materials proposed for embankment construction.
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Place all tailings fill material comprising the perimeter embankment in homogeneous horizontal layers not exceeding 300mm loose lift thickness. Each lift shall be compacted using a 12t heavy duty Vibratory Pad Foot Roller or an approved equivalent. Placement should be continuous. If a break in fill placement allows the exposed surface to dry, it should be lightly tyned, watered and compacted prior to fill placement recommencing. Each layer shall be compacted to achieve a density ratio greater than 95% of the maximum dry density - standard compaction as determined from laboratory test AS 1289.5.1.1. The actual number of passes of a 12t Vibratory Roller or an approved equivalent to achieve a density greater than 95% standard compaction (AS 1289.5.1.1) shall be determined on site using roller trials. Material considered suitable for embankment construction shall comprise tailings material having fines content (material finer than 75 microns) in excess of 25%. Cap the downstream face of the completed perimeter embankment with mine waste rock sourced from designated stockpiles. Raise the internal decant access causeway utilising traffic compacted mine waste sourced from designated stockpiles. Mine waste utilised in construction of the downstream face capping and decant access causeway shall be well graded rock fill, free of organic matter and other deleterious material, with a maximum particle size of 300mm and a fines content of at least 10%. Care should be taken that no voids are present within the placed material. All materials shall be stockpiled, transported and placed in such a manner as to minimise segregation. Raise and maintain the four (4) existing access ramps as directed by the Owner’s Representative. The location of any additional ramps shall be approved by the Owner’s Representative prior to commencement of these works. The additional ramps may be left in place at the discretion of the Principal. The Contractor shall assess the requirement for windrows during construction and ensure that they are maintained during construction to satisfy DMP regulatory criteria. The crest of the completed perimeter embankment shall be graded to the inside (upstream) of the storage at a 2% crossfall. A windrow of not less than 400mm height shall be constructed on both sides of the crest of all embankments. Sheet the crest of the perimeter embankment and decant access causeway with 100mm thick layer of gravel wearing course. The gravel shall be sourced from a location nominated by the Owner’s Representative and from reclaimed gravel wearing course material if deemed suitable for reuse. Allow for keeping water from the works during construction by shaping finished surfaces with a fall toward the centre of the storage. Construction of a surface water diversion channel (v-shaped) along toe of the southern extension perimeter embankment to allow flow towards the surface water management pond. Allow for maintaining the borrow areas free of large accumulations of water. 2.6. Decant Structure
The decant structures comprise standard precast slotted concrete pipes (Drawing No. MWP00345AV-06 and MWP00345AV-07).
Only clean select filter rock material with a low fines content shall be placed around the decant structures. Placed rock fill material shall be clean, fines-free (<3% passing 75µm), competent rock mine waste with a well-graded particle size distribution between 50 and 150mm. All rock shall be carefully placed to ensure the concrete pipes are not dislodged or damaged.
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The Contractor shall:
Transport all materials to construct the decant structures. Install slotted concrete pipes. Transport select decant filter rock from the designated source and place around the decant structures. Selected rock shall be sourced from a location nominated by the Owner’s Representative. 2.7. Pipework, Electrical and Instrumentation
The Contractor shall: Avoid damaging any pipework. Any pipework damaged by the Contractor shall be replaced at no additional cost to the Principal. Allow for others to remove any electrical installations or cables from the embankment as required by the Principal. The Principal will disconnect and remove electrical cables in advance of construction and will replace cables when that job lot has been completed. The Contractor shall avoid damaging the electrical installations. Any cables damaged by the Contractor shall be replaced at no additional cost to the Principal. Two (2) standpipe piezometers and eight (8) vibrating wire piezometers are located in the tailings storage. The locations of these are shown on Drawing No. MWP00345AV-01 to MWP00345AV- 05. The Contractor shall avoid any damage to the piezometers and the Principal shall be immediately notified of any such damage. Any piezometers damaged by the Contractor shall be replaced at no additional cost to the Principal. 2.8. Completion
The Contractor shall:
Clean up all rubbish, remove all plant and supply materials, trim all banks neatly, spread all excavated material not specified to be removed from the site and leave the site in a clean and tidy condition. Batter down the sides of borrow areas, as appropriate, for stability on completion of the work. Materials not considered suitable for use in the works shall be evenly spread over the surface of the borrow area. Provide an as built survey of the completed works in both electronic and hard copy within two weeks of the completion of the works.
3. Construction sequence
The Contractor shall liaise with the Principal to agree a sequence for the works. The Contractor shall endeavour to complete the raising of the perimeter embankments and decant access causeways in the sequence agreed and shall notify the Principal if the agreed programme cannot be achieved as the works progress.
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Cosmic Boy TSF Embankment Raising - Scope of Works
4. Inspection and testing 4.1. Inspection requirements
The Owner’s Representative will be entitled, at all times to inspect, examine and test the materials and workmanship being provided under the Contract. Such inspection, examination or testing, if made, shall not release the Contractor from any obligation under the Contract.
The Contractor shall co-operate with and provide full opportunity to the Owner’s Representative to monitor regularly the progress of the Works of the Contractor and his subcontractors to the detailed extent necessary to satisfy progress relative to the Construction Programme.
All pertinent information to enable the Owner’s Representative to determine the adequacy of the advance planning for material procurement, machine and manpower resources to meet the Construction Programme shall be made freely available to the Owner’s Representative.
These requirements shall be incorporated in orders placed with Subcontractors. 4.2. Testing plans
The Contractor shall provide not later than seven (7) days after award of Contract a certified testing programme. The testing programme shall include details of procedures, standards and acceptance levels and conform to the requirements of the specifications forming part of the Contract documentation.
Compliance tests shall be carried out by a qualified technician from a NATA registered laboratory. Compliance tests shall be carried out to such a degree as to satisfy the Owner’s Representative that the criteria on moisture content, compaction and material classification are met.
Compliance testing of compaction and moisture content shall be at the rate of not less than 1 test per layer per material type per 2,500m² (or 1 test per 750m³ ‘evenly’ spread through the fill, as determined by the Owner’s Representative). Particle size distribution and Atterberg limits tests shall be at the rate of not less than 1 test per 5,000m³.
The Contractor shall provide advance notice for the requirement for testing of placed material. The time allowance for testing will vary dependent on placement rates. Testing shall be undertaken so as not to impede construction progress. Under no circumstances shall placed material be covered prior to it being tested. The Contractor shall, at their own expense, rework or replace materials which do not meet the requirements of the Specification.
Table 1 - Compliance Testing Failure Remedial Action
Hilf Density Category Moisture Result Remedial Action Ratio Result Re-roll (No. of passes to be specified by A Fail by less than 1% Pass the Owner's Representative, max. 3) Pass, but not more than 1.0% B Fail by 1% or more Rip, re-water, re-roll and re-test wet of OMC Pass, but 1.0% or more wet of C Fail by 1% or more Rip, re-roll and re-test OMC Fail, but no more than 2.0% dry D Pass Rip, water, re-roll and re-test of OMC E Fail Fail Remove fill, replace and re-test Note: Requirements relate to a single result within a ‘lot’, not the average of the results for a ‘lot’
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Table 2 - Required Testing Frequency
Test Minimum Testing Frequency Test Description a. Locations Clayey Mine Waste Moisture Content E 1 per layer per 2500m² Atterberg Limits E Min 1 per 5000m³ Particle Size Distribution E Min 1 per 5000m³ Density Moisture Relation E 1 per 3 FDs (Standard or Modified compaction) Field Dry Density (FD) E 1 per layer per 2500m² Note: a. Location of tests on Embankment
5. Permits, licences and approvals
Further to the General Conditions of Contract, the Principal will obtain Department of Mines and Petroleum and Department of Environment Regulation Approval. All other necessary permits, licenses and approvals shall be obtained by the Contractor.
The Contractor will be responsible for providing all necessary health and safety information and records for supplies and equipment brought to site such as data sheets, emergency procedures, safety plans, operational plans as well as providing competency based records and police clearances for all site personnel. This includes recent drug screen test results.
6. Substitutions
The Contractor shall:
Not substitute any alternative to the equipment and materials included in the Scope of Works without the prior written consent of the Principal. Make diligent efforts to utilise the specified materials to be incorporated into the works but where the Contractor considers there are commercial or other advantages to be derived by the Principal, the Contractor may submit a proposal for a substitute material for approval by the Principal prior to commencement of the work. Such proposal for substitution shall be in writing and state reasons for and (if applicable) advantages of the substitute material. The Principal shall determine whether the substitute material will be permitted and such determination shall be binding and conclusive upon the Contractor. Approval of a substitution will be given as a variation under of the General Conditions of Contract incorporating any adjustment to the Contract Sum.
7. Principal clarification
Any services or materials not specifically identified as being provided by the Principal shall be provided by the Contractor.
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7.1. Communications
The Contractor shall allow for the provision of radio, telephone and facsimile facilities. Mobile coverage is available at the Cosmic Boy surroundings. 7.2. Accommodation
Accommodation and messing for the Contractor will be provided by the Principal. The Contractor shall supply a manning level programme to the Principal at the time of their tender submission. 7.3. Diesel fuel
Diesel fuel for the Contractor will be provided by the Principal. The Contractor shall advise what their expected fuel usage figures will be in the Construction Programme. 7.4. Flights
Flights may be available on a limited basis and will be supplied by the Principal. 7.5. Materials
The Principal shall provide fill material for use in the construction of the perimeter embankments, decant access causeways and decant structures for winning by the Contractor.
The Principal shall supply slotted concrete pipes for use in the construction of the decant towers. 7.6. Water
Construction water will be made available from a nominated standpipe. Access to the standpipe may not be exclusive to the Contractor. The Contractor shall determine the type and suitability of the water supplies for use in this Contract. The Contractor shall make their own arrangements for loading and hauling water. 7.7. Survey
The Principal will provide coordinates and levels of two survey marks within the vicinity of the works. The Contractor shall set out their works from these survey marks. The Contractor shall set up new marks as appropriate to provide accurate construction, survey control and quantity estimates.
8. Construction information
The Contractor shall provide a Construction Programme and indicate the following milestone dates:
Contract Award; Notice to Proceed; Initial mobilisation to site; Full mobilisation on site;
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Additional Milestone Dates; Principal Completion Date; and Final Completion Date.
The Contractor shall as part of their tender submission clearly outline the following:
Type and number of equipment to be mobilised to site; Equipment licensing or certification; Manning levels; Competency based records for personnel; Subcontractor or sub-hire equipment and organisations; Insurance certificates and certificates of currency; Name of nominated supervisory and first aid personnel; Relevant Chemical Data Sheets; and Safety Management Plans.
9. Estimate of quantities
A preliminary estimate of quantities has been provided to allow material requirements to be gauged for Construction. The figures have not been calculated by a Quantity Surveyor and are provided for convenience only. The Schedule of Quantities is included in this document as Appendix B.
10. Definition of terms
Contract: The agreement between the Principal and the Contractor.
Contractor: Person bound to execute the work under the Contract.
Owner’s Representative: Person appointed by the Principal in writing to represent the Principal.
Person: Includes a firm or body corporate or unincorporated or an individual.
Principal: Western Areas Ltd.
Principal Supplied Materials: Materials supplied by the Principal.
Scope of Works: This document.
Site: The lands and other places to be made available and any other lands and places made available to the Contractor by the Principal for the purpose of the Contract.
Subcontractor: Secondary person appointed by the Contractor to fulfil part/all of the Contract.
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Superintendent: Person appointed by the Principal as the Superintendent or other person from time to time appointed in writing by the Principal to be the Superintendent and notified as such in writing to the Contractor by the Principal.
Works: The whole of the work to be executed in accordance with the Contract, including variations provided for by the Contract, which by the Contract is to be handed over to the Principal.
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Important information about your Coffey Report
As a client of Coffey you should know that site subsurface conditions cause more construction problems than any other factor. These notes have been prepared by Coffey to help you interpret and understand the limitations of your report.
Your report is based on project specific criteria For this reason, owners should retain the services of Coffey through the development stage, to Your report has been developed on the basis of identify variances, conduct additional tests if your unique project specific requirements as required, and recommend solutions to problems understood by Coffey and applies only to the site encountered on site. investigated. Project criteria typically include the general nature of the project; its size and Your report will only give preliminary configuration; the location of any structures on the recommendations site; other site improvements; the presence of Your report is based on the assumption that the underground utilities; and the additional risk site conditions as revealed through selective point imposed by scope-of-service limitations imposed sampling are indicative of actual conditions by the client. Your report should not be used if throughout an area. This assumption cannot be there are any changes to the project without first substantiated until project implementation has asking Coffey to assess how factors that changed commenced and therefore your report subsequent to the date of the report affect the recommendations can only be regarded as report's recommendations. Coffey cannot accept preliminary. Only Coffey, who prepared the report, responsibility for problems that may occur due to is fully familiar with the background information changed factors if they are not consulted. needed to assess whether or not the report's Subsurface conditions can change recommendations are valid and whether or not changes should be considered as the project Subsurface conditions are created by natural develops. If another party undertakes the processes and the activity of man. For example, implementation of the recommendations of this water levels can vary with time, fill may be placed report there is a risk that the report will be on a site and pollutants may migrate with time. misinterpreted and Coffey cannot be held Because a report is based on conditions which responsible for such misinterpretation. existed at the time of subsurface exploration, Your report is prepared for specific purposes decisions should not be based on a report whose and persons adequacy may have been affected by time. Consult Coffey to be advised how time may have To avoid misuse of the information contained in impacted on the project. your report it is recommended that you confer with Coffey before passing your report on to another Interpretation of factual data party who may not be familiar with the background Site assessment identifies actual subsurface and the purpose of the report. Your report should conditions only at those points where samples are not be applied to any project other than that taken and when they are taken. Data derived from originally specified at the time the report was literature and external data source review, issued. sampling and subsequent laboratory testing are Interpretation by other design professionals interpreted by geologists, engineers or scientists to provide an opinion about overall site conditions, Costly problems can occur when other design their likely impact on the proposed development professionals develop their plans based on and recommended actions. Actual conditions may misinterpretations of a report. To help avoid differ from those inferred to exist, because no misinterpretations, retain Coffey to work with other professional, no matter how qualified, can reveal project design professionals who are affected by what is hidden by earth, rock and time. The actual the report. Have Coffey explain the report interface between materials may be far more implications to design professionals affected by gradual or abrupt than assumed based on the them and then review plans and specifications facts obtained. Nothing can be done to change the produced to see how they incorporate the report actual site conditions which exist, but steps can be findings. taken to reduce the impact of unexpected conditions.
Coffey MINEWPER00345AV 13 9 February 2016
Cosmic Boy TSF Embankment Raising - Scope of Works
Data should not be separated from the report* Rely on Coffey for additional assistance
The report as a whole presents the findings of the Coffey is familiar with a variety of techniques and site assessment and the report should not be approaches that can be used to help reduce risks copied in part or altered in any way. for all parties to a project, from design to Logs, figures, drawings, etc. are customarily construction. It is common that not all approaches included in our reports and are developed by will be necessarily dealt with in your site scientists, engineers or geologists based on their assessment report due to concepts proposed at interpretation of field logs (assembled by field that time. As the project progresses through design personnel) and laboratory evaluation of field towards construction, speak with Coffey to develop samples. alternative approaches to problems that may be of genuine benefit both in time and cost. These logs etc. should not under any circumstances be redrawn for inclusion in other Responsibility documents or separated from the report in any Reporting relies on interpretation of factual way. information based on judgement and opinion and Geoenvironmental concerns are not at issue has a level of uncertainty attached to it, which is far less exact than the design disciplines. This has Your report is not likely to relate any findings, often resulted in claims being lodged against conclusions, or recommendations about the consultants, which are unfounded. To help prevent potential for hazardous materials existing at the this problem, a number of clauses have been site unless specifically required to do so by the developed for use in contracts, reports and other client. Specialist equipment, techniques, and documents. Responsibility clauses do not transfer personnel are used to perform a geoenvironmental appropriate liabilities from Coffey to other parties assessment. Contamination can create major but are included to identify where Coffey's health, safety and environmental risks. If you have responsibilities begin and end. Their use is no information about the potential for your site to intended to help all parties involved to recognise be contaminated or create an environmental their individual responsibilities. Read all documents hazard, you are advised to contact Coffey for from Coffey closely and do not hesitate to ask any information relating to geoenvironmental issues. questions you may have.
* For further information on this aspect reference should be made to "Guidelines for the Provision of Geotechnical information in Construction Contracts" published by the Institution of Engineers Australia, National headquarters, Canberra, 1987.
Coffey MINEWPER00345AV 14 9 February 2016
Appendix A - Drawings
notes: 6 391000mN 6 391200mN 6 391400mN 6 391600mN 6 391800mN
757 800 mE 757 800 mE NORTH END OFSTAGE 2TAILINGSBEACHCONTOURS (1m) EXISTING SURFACECONTOURS (1m) CULVERT
407mRL 403mRL
SURFACE WATERMANAGEMENTPOND
06 A CULVERT
758 000 mE 758 000 mE EXISTING STAGE2EMBANKMENT rev no READ-OUT UNIT A 0 1 CRESTATRL415m CABLE AND STANDPIPE PIEZOMETERLOCATIONS
ISSUED FORCLIENT REVIEW ISSUED WITHSCOPEOFWORKS DOCUMENT SURFACE WATERMANAGEMENT INFRASTRUCTUREADDED
06 B TAILINGS RECLAIMAREA
revision note
06 C
758 200 mE 758 200 mE TAILINGS STORAGE
407mRL
399mRL COSMIC BOY 408mRL FACILITY 411mRL PIEZOMETER LOCATIONS VIBRATING WIRE 27/10/2014 22/12/2014 09/02/2016 VIBRATING WIREPIEZOMETERLOCATIONS date 409mRL approved EXISTING STAGE2EMBANKMENT CH CH CH CREST ATRL415m
412mRL READ-OUT UNIT CABLE AND Date: Drawn:
Original size: Scale: 410mRL Approved: 09/02/2016 1:1500 FvdL CH A1 411mRL 408mRL 413mRL
758 400 mE 758 400 mE STANDPIPE PIEZOMETERLOCATIONS
414mRL Project no: Project: Client: Title: DWG: F:\MINE\Projects\Western AreasNL\MINEWPER00345AV_CosmicBoyTSFRaising\DWG\MWP00345AV-01.dwg
MWP00345AV
COSMIC BOYTAILINGSSTORAGE FACILITY
06 GENERAL ARRANGEMENT STAGE2 A PROPOSED EMBANKMENTRAISES WESTERN AREASLTD
412mRL Dwg no: MWP00345AV-01 410mRL 6 391800mN 6 391000mN 6 391200mN 6 391400mN 6 391600mN Rev:
1 758 600 mE 758 600 mE notes: 6 391000mN 6 391200mN 6 391400mN 6 391600mN 6 391800mN
757 800 mE 757 800 mE NORTH CULVERT END OFSTAGE 3TAILINGSBEACHCONTOURS (1m) EXISTING SURFACECONTOURS (1m) STAGE 3EMBANKMENT DESIGN SURFACECONTOURS(1m) PROPOSED STAGE3ACCESS RAMP RAISING(GRADE1:8)
407mRL 403mRL
SURFACE WATERMANAGEMENTPOND
06 A PROPOSED STAGE3ACCESS RAMP RAISING(GRADE1:8) CULVERT
758 000 mE 758 000 mE PROPOSED STAGE3EMBANKMENT rev no READ-OUT UNIT A 0 1 CREST ATRL417m CABLE AND STANDPIPE PIEZOMETERLOCATIONS
ISSUED FORCLIENT REVIEW ISSUED WITHSCOPEOFWORKS DOCUMENT SURFACE WATERMANAGEMENT INFRASTRUCTUREADDED
06 B DECANT ACCESSWAYRAISING PROPOSED STAGE3 TAILINGS RECLAIMAREA
revision note 06
758 200 mE C 758 200 mE TAILINGS STORAGE
407mRL
399mRL COSMIC BOY FACILITY 408mRL 413mRL DECANT STRUCTURERAISING PROPOSED STAGE3 PIEZOMETER LOCATIONS VIBRATING WIRE 27/10/2014 22/12/2014 09/02/2016 VIBRATING WIREPIEZOMETERLOCATIONS date 409mRL approved PROPOSED STAGE3EMBANKMENT CH CH CH 414mRL CREST ATRL417m READ-OUT UNIT CABLE AND Date: Drawn:
Original size: Scale: 410mRL Approved: 09/02/2016 1:1500 FvdL CH A1 411mRL 415mRL 408mRL
758 400 mE 758 400 mE STANDPIPE PIEZOMETERLOCATIONS
416mRL Project no: Project: Client: Title: DWG: F:\MINE\Projects\Western AreasNL\MINEWPER00345AV_CosmicBoyTSFRaising\DWG\MWP00345AV-02.dwg
MWP00345AV
COSMIC BOYTAILINGSSTORAGE FACILITY
06 GENERAL ARRANGEMENT STAGE3 A PROPOSED EMBANKMENTRAISES WESTERN AREASLTD RAMP RAISING(GRADE1:8) PROPOSED STAGE3ACCESS RAMP RAISING(GRADE1:8) PROPOSED STAGE3ACCESS 412mRL Dwg no: MWP00345AV-02 410mRL 6 391800mN 6 391000mN 6 391200mN 6 391400mN 6 391600mN Rev:
1 758 600 mE 758 600 mE notes: 6 391000mN 6 391200mN 6 391400mN 6 391600mN 6 391800mN
757 800 mE 757 800 mE NORTH SURFACE WATERMANAGEMENTPOND EMBANKMENT CRESTATRL413.5m EXTENSION SOUTHSTARTER CULVERT END OFEXT SOUTHSTARTEREMBANKMENT TAILINGS EXTENSION SOUTHSTARTER EMBANKMENTDESIGN EXISTING SURFACECONTOURS (1m) BEACH CONTOURS (1m) SURFACE CONTOURS(1m)
407mRL 403mRL 07 D CULVERT
758 000 mE 758 000 mE rev no READ-OUT UNIT A 0 1 CABLE AND STANDPIPE PIEZOMETERLOCATIONS ISSUED FORCLIENT REVIEW ISSUED WITHSCOPEOFWORKS DOCUMENT SURFACE WATERMANAGEMENT INFRASTRUCTUREADDED revision note FACILITY -EXTENSIONSOUTH TAILINGS STORAGE COSMIC BOY
758 200 mE 758 200 mE TAILINGS STORAGE
407mRL
399mRL COSMIC BOY FACILITY PROPOSED EXTSOUTH CREST RL413.5m STARTER DECANTSTRUCTURE
410mRL PIEZOMETER LOCATIONS VIBRATING WIRE 27/10/2014 22/12/2014 09/02/2016 VIBRATING WIREPIEZOMETERLOCATIONS date 412mRL
411mRL approved
CH CH CH 414mRL Date: Drawn: Original size: Scale: Approved: 09/02/2016 1:1500 FvdL CH A1 415mRL 408mRL
758 400 mE 758 400 mE STANDPIPE PIEZOMETERLOCATIONS VWP CABLE
416mRL Project no: Project: Client: Title: GENERAL ARRANGEMENT EXTSOUTHSTARTER EMBANKMENT DWG: F:\MINE\Projects\Western AreasNL\MINEWPER00345AV_CosmicBoyTSFRaising\DWG\MWP00345AV-03.dwg MWP00345AV COSMIC BOYTAILINGSSTORAGE FACILITY PROPOSED EMBANKMENTRAISES WESTERN AREASLTD
412mRL Dwg no: VWP READ-OUTUNIT MWP00345AV-03 410mRL 6 391800mN 6 391000mN 6 391200mN 6 391400mN 6 391600mN Rev:
1 758 600 mE 758 600 mE notes: 6 391000mN 6 391200mN 6 391400mN 6 391600mN 6 391800mN
757 800 mE 757 800 mE NORTH SURFACE WATERMANAGEMENTPOND CULVERT END OFSTAGE 4TAILINGSBEACHCONTOURS (1m) EXISTING SURFACECONTOURS (1m) STAGE 4EMBANKMENT DESIGN SURFACECONTOURS(1m) PROPOSED STAGE4ACCESS RAMP RAISING(GRADE1:8)
407mRL 403mRL
06 A PROPOSED STAGE4ACCESS RAMP RAISING(GRADE1:8) CULVERT
758 000 mE 758 000 mE STAGE 4EMBANKMENT rev no CRESTATRL419m READ-OUT UNIT A 0 1 CABLE AND STANDPIPE PIEZOMETERLOCATIONS
ISSUED FORCLIENT REVIEW ISSUED WITHSCOPEOFWORKS DOCUMENT SURFACE WATERMANAGEMENT INFRASTRUCTUREADDED
06 B DECANT ACCESSWAYRAISING PROPOSED STAGE4 PROPOSED STAGE4ACCESS revision note RAMP RAISING(GRADE1:8) FACILITY -EXTENSIONSOUTH TAILINGS STORAGE
COSMIC BOY 06
758 200 mE C 758 200 mE TAILINGS STORAGE
407mRL COSMIC BOY
399mRL FACILITY 415mRL DECANT STRUCTURERAISING PROPOSED STAGE4
410mRL PIEZOMETER LOCATIONS VIBRATING WIRE 27/10/2014 22/12/2014 09/02/2016 VIBRATING WIREPIEZOMETERLOCATIONS date 412mRL
411mRL
approved 416mRL CH CH CH CREST ATRL419m STAGE 4EMBANKMENT Date: Drawn: Original size: Scale: Approved: VWP CABLE 09/02/2016
1:1500 417mRL FvdL CH A1 408mRL
758 400 mE 758 400 mE STANDPIPE PIEZOMETERLOCATIONS
418mRL Project no: Project: Client: Title: DWG: F:\MINE\Projects\Western AreasNL\MINEWPER00345AV_CosmicBoyTSFRaising\DWG\MWP00345AV-04.dwg MWP00345AV COSMIC BOYTAILINGSSTORAGE FACILITY GENERAL ARRANGEMENT STAGE4 PROPOSED EMBANKMENTRAISES RAMP RAISING(GRADE1:8) PROPOSED STAGE4ACCESS WESTERN AREASLTD 06 RAMP RAISING(GRADE1:8) PROPOSED STAGE4ACCESS A 412mRL Dwg no: VWP READ-OUTUNIT MWP00345AV-04 410mRL 6 391800mN 6 391000mN 6 391200mN 6 391400mN 6 391600mN Rev:
1 758 600 mE 758 600 mE notes: 6 391000mN 6 391200mN 6 391400mN 6 391600mN 6 391800mN
757 800 mE 757 800 mE NORTH SURFACE WATERMANAGEMENTPOND EMBANKMENT CRESTATRL416m CULVERT EXTENSION SOUTHSTAGE1 END OFEXT SOUTHSTAGE1EMBANKMENT TAILINGS EXTENSION SOUTHSTAGE 1EMBANKMENTDESIGN EXISTING SURFACECONTOURS (1m) BEACH CONTOURS (1m) SURFACE CONTOURS(1m)
407mRL 403mRL 07 D CULVERT
758 000 mE 758 000 mE rev no READ-OUT UNIT A 0 1 CABLE AND STANDPIPE PIEZOMETERLOCATIONS ISSUED FORCLIENT REVIEW ISSUED WITHSCOPEOFWORKS DOCUMENT SURFACE WATERMANAGEMENT INFRASTRUCTUREADDED revision note FACILITY -EXTENSIONSOUTH TAILINGS STORAGE COSMIC BOY
758 200 mE 758 200 mE TAILINGS STORAGE
407mRL COSMIC BOY
399mRL PROPOSED EXTSOUTH CREST RL416m STAGE 1DECANTSTRUCTURE FACILITY 413mRL 414mRL 415mRL PIEZOMETER LOCATIONS VIBRATING WIRE 27/10/2014 22/12/2014 09/02/2016 VIBRATING WIREPIEZOMETERLOCATIONS date
approved 416mRL CH CH CH Date: Drawn: Original size: Scale: Approved: 09/02/2016
1:1500 417mRL FvdL CH A1 408mRL STANDPIPE PIEZOMETERLOCATIONS
758 400 mE 758 400 mE VWP CABLE
418mRL Project no: Project: Client: Title: GENERAL ARRANGEMENT EXTSOUTHSTAGE 1EMBANKMENT DWG: F:\MINE\Projects\Western AreasNL\MINEWPER00345AV_CosmicBoyTSFRaising\DWG\MWP00345AV-05.dwg MWP00345AV COSMIC BOYTAILINGSSTORAGE FACILITY PROPOSED EMBANKMENTRAISES WESTERN AREASLTD
412mRL Dwg no: VWP READ-OUTUNIT MWP00345AV-05 410mRL 6 391800mN 6 391000mN 6 391200mN 6 391400mN 6 391600mN Rev:
1 758 600 mE 758 600 mE 7000 DOWNSTREAM UPSTREAM 6500 100mm GRAVEL SHEETING 500 MINE WASTE WIDTH AT CREST SAFETY BUND TAILINGS DISTRIBUTION AND MINIMUM 400mm HIGH RETURN WATER PIPELINES
EMBANKMENT RAISE 4 CREST RL 419 m NON-ACID FORMING WASTE CAPPING
2000 1 1.5 RAISE 4 EMBANKMENT 3 1 PROPOSED DEPOSITED TAILINGS 2500 4500 COMPACTED TAILINGS (PROPOSED) EMBANKMENT RAISE 3 CREST RL 417 m NON-ACID FORMING WASTE CAPPING
2000 1 RAISE 3 EMBANKMENT 1.5 3 COMPACTED TAILINGS (PROPOSED) 2500 4500 1 PROPOSED DEPOSITED TAILINGS EMBANKMENT RAISE 2 CREST RL 415 m NON-ACID FORMING WASTE CAPPING 1 3 RAISE 2 EMBANKMENT 1.5 2500 5500 COMPACTED TAILINGS (EXISTING) 1 PROPOSED DEPOSITED TAILINGS EMBANKMENT RAISE 1 CREST RL 413 m NON-ACID FORMING WASTE CAPPING (EXISTING) 1.5 1 RAISE 1 EMBANKMENT 3 COMPACTED TAILINGS (EXISTING) 1 DEPOSITED TAILINGS STARTER CREST RL 411 m
3 1.5 STARTER EMBANKMENT 1 1 WASTE ROCK (EXISTING) DEPOSITED TAILINGS
EXISTING REHABILITATED SURFACE (VARIES) 1 1
EXISTING IN SITU WASTE ROCK / TOPSOIL COVER EXISTING TAILINGS 1000 400 CUT-OFF TRENCH 1000 COMPACTED TAILINGS (EXISTING)
3000
A PERIMETER EMBANKMENT 1,2,4 TYPICAL SECTION SCALE 1:100
REMOVE EXISTING WINCH AND REINSTALL REMOVE EXISTING SAFETY GRATE AND ON COMPLETED DECANT STRUCTURE REINSTALL ON COMPLETED DECANT STRUCTURE
8000 MIN
6000 MIN 100mm GRAVEL SHEETING SAFETY BUND 100mm GRAVEL SHEETING MINIMUM 400mm HIGH MINE WASTE SAFETY BUND STAGE 4 CREST RL VARIES (MINIMUM 417 m) STAGE 4 CREST RL 417 m MINIMUM 400mm HIGH COARSE SELECT FILTER ROCK
1.5 STAGE 4 DECANT ACCESS 1.5 1.5 RAISE 4 DECANT 1.5 1 CAUSEWAY (PROPOSED) 1 1 STRUCTURE (PROPOSED) 1 PROPOSED DEPOSITED TAILINGS PROPOSED DEPOSITED TAILINGS PROPOSED DEPOSITED TAILINGS PROPOSED DEPOSITED TAILINGS STAGE 3 CREST RL VARIES (MINIMUM 415 m) STAGE 3 CREST RL 415 m
STAGE 3 DECANT ACCESS RAISE 3 DECANT CAUSEWAY (PROPOSED) STRUCTURE (PROPOSED) PROPOSED DEPOSITED TAILINGS PROPOSED DEPOSITED TAILINGS PROPOSED DEPOSITED TAILINGS PROPOSED DEPOSITED TAILINGS STAGE 2 CREST RL VARIES (MINIMUM 413 m) STAGE 2 CREST RL 413 m STAGE 2 DECANT ACCESS STAGE 1 CREST RL VARIES (MINIMUM 412) CAUSEWAY (EXISTING) RAISE 2 DECANT DEPOSITED TAILINGS SURFACE (VARIES) STAGE 1 DECANT ACCESS DEPOSITED TAILINGS SURFACE (VARIES) STRUCTURE (EXISTING) STARTER CREST RL 411 m CAUSEWAY (EXISTING) STARTER CREST RL 411 m DEPOSITED TAILINGS DEPOSITED TAILINGS DEPOSITED TAILINGS SURFACE (VARIES) DEPOSITED TAILINGS SURFACE (VARIES)
STARTER DECANT STRUCTURE (EXISTING) STARTER DECANT ACCESS DEPOSITED TAILINGS CAUSEWAY (EXISTING) DEPOSITED TAILINGS DEPOSITED TAILINGS DEPOSITED TAILINGS
HUMES DECANT PIPE [ :$// 839&&/$666/277('3,3( 18 SLOT (3 RINGS) per 1200mm OR APPROVED EQUIVALENT
B DECANT ACCESS CAUSEWAY C DECANT STRUCTURE 1,2,4 TYPICAL SECTION 1,2,4 TYPICAL SECTION SCALE 1:100 SCALE 1:100
Client: notes: Drawn: FvdL WESTERN AREAS LTD Project: Approved: CH COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date: 22/12/2014 0 ISSUED WITH SCOPE OF WORKS DOCUMENT 22/12/2014 CH Title: A ISSUED FOR CLIENT REVIEW 27/10/2014 CH Scale: 1:100 TYPICAL SECTIONS - SHEET 1 OF 2
Original size: Project no: Dwg no: Rev: DWG: F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\DWG\MWP00345AV-06.dwg rev no revision note date approved A1 MWP00345AV MWP00345AV-06 0 DOWNSTREAM UPSTREAM 7000 100mm GRAVEL SHEETING SAFETY BUND TAILINGS DISTRIBUTION AND 1200 5800 MINIMUM 400mm HIGH RETURN WATER PIPELINES
STAGE 1 CREST RL 416 m
NON-ACID FORMING WASTE CAPPING
1.5 1 STAGE 1 EMBANKMENT 3 COMPACTED TAILINGS (PROPOSED) 1 PROPOSED DEPOSITED TAILINGS STARTER CREST RL 413.5 m
3 1.5 STARTER EMBANKMENT 1 1 WASTE ROCK (PROPOSED) PROPOSED DEPOSITED TAILINGS
NATURAL GROUND SURFACE (VARIES) 1 1 1000 CUT-OFF TRENCH 1000 COMPACTED TAILINGS
3000
D PERIMETER EMBANKMENT 3,5 TYPICAL SECTION SCALE 1:100
INSTALL WINCH ON COMPLETED INSTALL SAFETY GRATE ON DECANT STRUCTURE COMPLETED DECANT STRUCTURE
100mm GRAVEL SHEETING 100mm GRAVEL SHEETING 8000 MIN SAFETY BUND 6000 MIN SAFETY BUND MINIMUM 400mm HIGH MINIMUM 400mm HIGH MINE WASTE COARSE SELECT FILTER ROCK STAGE 1 CREST RL 416 m STAGE 1 CREST RL 416 m
1.5 1.5 1 STAGE 1 DECANT ACCESS 1 1.5 STAGE 1 DECANT 1.5 PROPOSED DEPOSITED TAILINGS CAUSEWAY (PROPOSED) PROPOSED DEPOSITED TAILINGS 1 STRUCTURE (PROPOSED) 1 PROPOSED DEPOSITED TAILINGS PROPOSED DEPOSITED TAILINGS STARTER CREST RL 413.5 m STARTER CREST RL 413.5 m
STARTER DECANT STRUCTURE (PROPOSED) STARTER DECANT ACCESS PROPOSED DEPOSITED TAILINGS CAUSEWAY (PROPOSED) PROPOSED DEPOSITED TAILINGS PROPOSED DEPOSITED TAILINGS PROPOSED DEPOSITED TAILINGS
HUMES DECANT PIPE [ :$// 839&&/$666/277('3,3( 18 SLOT (3 RINGS) per 1200mm OR APPROVED EQUIVALENT
E DECANT ACCESS CAUSEWAY F DECANT STRUCTURE 3,5 TYPICAL SECTION 3,5 TYPICAL SECTION SCALE 1:100 SCALE 1:100
Client: notes: Drawn: FvdL WESTERN AREAS LTD Project: Approved: CH COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date: 22/12/2014 0 ISSUED WITH SCOPE OF WORKS DOCUMENT 22/12/2014 CH Title: A ISSUED FOR CLIENT REVIEW 27/10/2014 CH Scale: 1:100 TYPICAL SECTIONS - SHEET 2 OF 2
Original size: Project no: Dwg no: Rev: DWG: F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\DWG\MWP00345AV-07.dwg rev no revision note date approved A1 MWP00345AV MWP00345AV-07 0 notes: 6 391000mN 6 391200mN 6 391400mN 6 391600mN 6 391800mN 6 392000mN 6 392200mN 6 392400mN 6 390800mN
757 600 mE 757 600 mE SURFACE CONTOURS(1m) (MONITORING BORE01)
757 800 mE 757 800 mE
407mRL 403mRL rev no A 0 ISSUED FORCLIENTREVIEW ISSUED WITHSCOPEOFWORKS DOCUMENT
758 000 mE 758 000 mE FACILITY -EXTENSIONSOUTH revision note TAILINGS STORAGE TAILINGS STORAGE COSMIC BOY COSMIC BOY FACILITY 758 200 mE 758 200 mE 407mRL 399mRL 413mRL
414mRL 415mRL
416mRL 10/11/2014 22/12/2014 date
417mRL
408mRL approved CH CH 758 400 mE 758 400 mE Date: Drawn: Original size: Scale: Approved:
418mRL 22/12/2014 1:2500 FvdL CH A1
412mRL
410mRL
758 600 mE 758 600 mE Project no: Project: Client: Title: DWG: F:\MINE\Projects\Western AreasNL\MINEWPER00345AV_CosmicBoyTSFRaising\DWG\MWP00345AV-08.dwg MWP00345AV COSMIC BOYTAILINGSSTORAGE FACILITY PROPOSED EMBANKMENTRAISES MONITORING BORELOCATIONS WESTERN AREASLTD NORTH Dwg no: MWP00345AV-08 758 800 mE 758 800 mE 6 392200mN 6 392400mN 6 390800mN 6 391000mN 6 391200mN 6 391400mN 6 391600mN 6 391800mN 6 392000mN Rev: 0
Appendix B - Schedule of Quantities
PROJECT: COSMIC BOY TAILINGS STORAGE FACILITY STAGE 3 EMBANKMENT RAISE Date 4-Nov-14 Project No MWP00345AV CLIENT: WESTERN AREAS LTD File MWP00345AV SOQ Subject Quantities LOCATION: FORRESTANIA NICKEL PROJECT Revision A
SUBJECT: SCHEDULE OF QUANTITIES
Item Description Unit Quantity Rate Amount
1.0 SITE ESTABLISHMENT
1.1 Including all preliminaries, insurances etc, mobilisation, demobilisation, borrow $ - management, maintenance of existing tracks
ITEM 1.0 TOTAL $ -
2.0 EARTHWORKS
Perimeter Embankment
2.1 Remove existing wearing course material to designated stockpile(s) m³ 1,350 $ -
2.2 Prepare perimeter embankment foundation area (clear, remove unsuitable material, m² 35,100 $ - scarify and moisture condition), including existing embankment crest area and tailings beach area forming embankment raise foundation
2.3 Borrow, transport, place, moisture condition and compact tailings to perimeter m³ 50,400 $ - embankment
2.4 Borrow, transport, place and compact non acid forming (NAF) waste material to m³ 8,500 $ - perimeter embankment downstream face
2.5 Construct safety windrows (minimum 400mm height) along edges of perimeter m 3,675 $ - embankment
2.6 Place 100mm wearing course on embankment crest m³ 1,300 $ -
2.7 Raise existing access ramps as directed no. 4 $ -
Decant
2.8 Remove existing wearing course material to designated stockpile(s) m³ 250 $ -
2.9 Borrow, transport, place and compact mine waste to decant access causeway m³ 9,000 $ -
2.10 Construct safety windrows (minimum 400mm height) along edges of decant access m 650 $ - causeway
2.11 Place 100mm wearing course on decant access causeway crest m³ 250 $ -
2.12 Install slotted concrete well liners to decant tower no. 2 $ -
2.13 Borrow, transport and place clean select filter rock around decant tower m³ 1,000 $ -
ITEM 2.0 TOTAL $ -
TOTAL COST $ -
15% CONTINGENCY $ -
TOTAL BUDGET COST $ -
F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Report Preparation\Scope of Works\Text\MWP00345AV SOQ Rev A.xlsx PROJECT: COSMIC BOY TAILINGS STORAGE FACILITY SOUTH EXTENSION STARTER Date 9-Feb-16 EMBANKMENT Project No MWP00345AV CLIENT: WESTERN AREAS LTD File MWP00345AV SOQ Subject Quantities LOCATION: FORRESTANIA NICKEL PROJECT Revision A
SUBJECT: SCHEDULE OF QUANTITIES
Item Description Unit Quantity Rate Amount
1.0 SITE ESTABLISHMENT
1.1 Including all preliminaries, insurances etc, mobilisation, demobilisation, borrow $ - management, maintenance of existing tracks
ITEM 1.0 TOTAL $ -
2.0 EARTHWORKS
Perimeter Embankment
2.1 Excavate cut-off trench along upstream toe of perimeter embankment m³ 5,600 $ -
2.2 Prepare perimeter embankment foundation area (clear, remove unsuitable material, m² 44,500 $ - scarify and moisture condition), including existing embankment crest area and tailings beach area forming embankment raise foundation
2.3 Borrow, transport, place, moisture condition and compact tailings to perimeter m³ 41,600 $ - embankment
2.4 Borrow, transport, place and compact clayey mine waste material to perimeter m³ 108,500 $ - embankment
2.5 Construct safety windrows (minimum 400mm height) along edges of perimeter m 2,880 $ - embankment
2.6 Place 100mm wearing course on embankment crest m³ 1,000 $ -
2.7 Construct access ramps as directed no. 2 $ -
2.8 Construct surface water diversion channel (v-shaped) along toe of the southern m 1,300 $ - extension perimeter embankment
Decant
2.9 Remove existing wearing course material to designated stockpile(s) m³ 0 $ -
2.10 Borrow, transport, place and compact mine waste to decant access causeway m³ 3,000 $ -
2.11 Construct safety windrows (minimum 400mm height) along edges of decant access m 110 $ - causeway
2.12 Place 100mm wearing course on decant access causeway crest m³ 35 $ -
2.13 Install slotted concrete well liners to decant tower (including concrete base) no. 5 $ -
2.14 Borrow, transport and place clean select filter rock around decant tower m³ 600 $ -
ITEM 2.0 TOTAL $ -
TOTAL COST $ -
15% CONTINGENCY $ -
TOTAL BUDGET COST $ - PROJECT: COSMIC BOY TAILINGS STORAGE FACILITY STAGE 4 EMBANKMENT RAISE Date 4-Nov-14 Project No MWP00345AV CLIENT: WESTERN AREAS LTD File MWP00345AV SOQ Subject Quantities LOCATION: FORRESTANIA NICKEL PROJECT Revision A
SUBJECT: SCHEDULE OF QUANTITIES
Item Description Unit Quantity Rate Amount
1.0 SITE ESTABLISHMENT
1.1 Including all preliminaries, insurances etc, mobilisation, demobilisation, borrow $ - management, maintenance of existing tracks
ITEM 1.0 TOTAL $ -
2.0 EARTHWORKS
Perimeter Embankment
2.1 Remove existing wearing course material to designated stockpile(s) m³ 1,300 $ -
2.2 Prepare perimeter embankment foundation area (clear, remove unsuitable material, m² 34,200 $ - scarify and moisture condition), including existing embankment crest area and tailings beach area forming embankment raise foundation
2.3 Borrow, transport, place, moisture condition and compact tailings to perimeter m³ 49,250 $ - embankment
2.4 Borrow, transport, place and compact non acid forming (NAF) waste material to m³ 8,000 $ - perimeter embankment downstream face
2.5 Construct safety windrows (minimum 400mm height) along edges of perimeter m 3,575 $ - embankment
2.6 Place 100mm wearing course on embankment crest m³ 1,250 $ -
2.7 Raise existing access ramps as directed no. 4 $ -
Decant
2.8 Remove existing wearing course material to designated stockpile(s) m³ 250 $ -
2.9 Borrow, transport, place and compact mine waste to decant access causeway m³ 9,000 $ -
2.10 Construct safety windrows (minimum 400mm height) along edges of decant access m 650 $ - causeway
2.11 Place 100mm wearing course on decant access causeway crest m³ 250 $ -
2.12 Install slotted concrete well liners to decant tower no. 2 $ -
2.13 Borrow, transport and place clean select filter rock around decant tower m³ 1,000 $ -
ITEM 2.0 TOTAL $ -
TOTAL COST $ -
15% CONTINGENCY $ -
TOTAL BUDGET COST $ - PROJECT: COSMIC BOY TAILINGS STORAGE FACILITY SOUTH EXTENSION STAGE 1 Date 4-Nov-14 EMBANKMENT RAISE Project No MWP00345AV CLIENT: WESTERN AREAS LTD File MWP00345AV SOQ Subject Quantities LOCATION: FORRESTANIA NICKEL PROJECT Revision A
SUBJECT: SCHEDULE OF QUANTITIES
Item Description Unit Quantity Rate Amount
1.0 SITE ESTABLISHMENT
1.1 Including all preliminaries, insurances etc, mobilisation, demobilisation, borrow $ - management, maintenance of existing tracks
ITEM 1.0 TOTAL $ -
2.0 EARTHWORKS
Perimeter Embankment
2.1 Remove existing wearing course material to designated stockpile(s) m³ 1,000 $ -
2.2 Prepare perimeter embankment foundation area (clear, remove unsuitable material, m² 30,800 $ - scarify and moisture condition), including existing embankment crest area and tailings beach area forming embankment raise foundation
2.3 Borrow, transport, place, moisture condition and compact tailings to perimeter m³ 49,000 $ -
2.4 Borrow, transport, place and compact non acid forming (NAF) waste material to m³ 10,450 $ - perimeter embankment downstream face
2.5 Construct safety windrows (minimum 400mm height) along edges of perimeter m 2,820 $ -
2.6 Place 100mm wearing course on embankment crest m³ 1,000 $ -
2.7 Raise existing access ramps as directed no. 2 $ -
Decant
2.8 Remove existing wearing course material to designated stockpile(s) m³ 35 $ -
2.9 Borrow, transport, place and compact mine waste to decant access causeway m³ 1,500 $ -
2.10 Construct safety windrows (minimum 400mm height) along edges of decant access m 110 $ - causeway
2.11 Place 100mm wearing course on decant access causeway crest m³ 35 $ -
2.12 Install slotted concrete well liners to decant tower no. 2 $ -
2.13 Borrow, transport and place clean select filter rock around decant tower m³ 500 $ -
ITEM 2.0 TOTAL $ -
TOTAL COST $ -
15% CONTINGENCY $ -
TOTAL BUDGET COST $ -
This page has been left intentionally blank
Appendix B - Geotechnical Investigation Report
Appendix C - Monitoring Instrumentation Data
Forrestania Nickel Project Standing Water Levels - Cosmic Boy TSF
MB01 MB02 MB03 MB04 MB05 MB06 MB07 MB08 MB09 MB10 MB11 Easting 758117 758115 758330 758451 758248 757866 758563 758793 757639 757977 757972 Northing 6392058 6392238 6392061 6392257 6392551 6391924 6391887 6391636 6391368 6390673 6390669
R.L. (m) 399.107 397.985 399.411 397.610 396.605 402.693 406.012 415.812 410.403 410.296 410.116
Date MB01 MB02 MB03 MB04 MB05 MB06 MB07 MB08 MB09 MB10 MB11 Jan-13 6.099 11.453 8.520 9.393 14.743 8.320 17.985 34.863 24.450 20.262 20.179 Feb-13 6.775 11.596 8.590 9.499 14.603 8.295 18.951 33.886 23.910 20.356 20.180 Mar-13 6.672 11.569 8.580 9.522 14.603 8.295 18.952 33.742 23.899 20.231 20.204 Apr-13 6.300 11.860 8.390 9.400 #N/A 8.360 19.020 33.844 23.850 20.088 20.170 May-13 5.656 11.659 8.309 9.196 14.589 7.989 17.798 33.429 23.620 19.921 19.986 Jun-13 6.419 11.591 8.204 8.989 14.465 7.985 17.619 33.391 23.620 19.921 19.986 Jul-13 5.886 11.413 8.245 9.110 #N/A 8.103 17.615 33.605 23.982 20.105 20.100 Aug-13 6.735 11.349 8.020 8.789 14.429 7.650 17.562 33.459 23.405 20.190 20.070 Sep-13 6.930 11.200 8.000 8.655 14.301 7.580 17.440 33.353 23.335 #N/A #N/A Oct-13 6.761 11.080 7.930 8.635 14.220 7.483 17.487 33.348 23.265 19.900 19.900 Nov-13 7.657 10.723 7.955 8.550 14.602 7.531 17.200 33.329 23.230 19.870 19.855 Dec-13 6.888 10.594 8.061 8.857 14.082 7.552 17.064 33.264 23.079 19.784 19.777 Jan-14 7.421 10.482 8.059 8.639 14.118 7.351 #N/A 33.270 23.055 19.750 19.695 Feb-14 7.341 10.566 8.196 8.765 14.157 7.652 16.982 33.274 23.043 19.776 19.771 Mar-14 8.030 10.646 8.235 8.755 14.100 7.652 17.040 33.325 23.010 19.790 19.770 Apr-14 8.394 #N/A #N/A #N/A #N/A 7.765 #N/A #N/A #N/A #N/A #N/A May-14 8.320 10.789 7.705 8.834 14.290 7.624 16.955 33.276 23.020 19.755 19.750 Jun-14 6.763 11.015 7.715 8.605 14.222 7.555 16.810 33.236 22.700 19.715 19.705 Cosmic Boy TSF - FS North: VWPs
Plot Latest Unit
VWP01_mH2O: Cosmic Boy TSF - FS 4.064 mH2O North
VWP02_mH2O: Cosmic Boy TSF - FS 4.570 mH2O North
VWP03_mH2O: Cosmic Boy TSF - FS 0.150 mH2O North
VWP04_mH2O: Cosmic Boy TSF - FS -0.115 mH2O North Cosmic Boy TSF - FS North: VWPs
Plot Latest Unit
VWP01_mRL: Cosmic Boy TSF - FS 402.8 mRL North
VWP02_mRL: Cosmic Boy TSF - FS 403.1 mRL North
VWP03_mRL: Cosmic Boy TSF - FS 409.9 mRL North
VWP04_mRL: Cosmic Boy TSF - FS 409.6 mRL North Cosmic Boy TSF - FS South: VWPs
Plot Latest Unit
VWP05_mH2O: Cosmic Boy TSF - FS 0.00881 mH2O South
VWP06_mH2O: Cosmic Boy TSF - FS 0.695 mH2O South
VWP07_mH2O: Cosmic Boy TSF - FS -0.184 mH2O South
VWP08_mH2O: Cosmic Boy TSF - FS 0.630 mH2O South Cosmic Boy TSF - FS South: VWPs
Plot Latest Unit
VWP05_mRL: Cosmic Boy TSF - FS 409.8 mRL South
VWP06_mRL: Cosmic Boy TSF - FS 410.4 mRL South
VWP07_mRL: Cosmic Boy TSF - FS 404.3 mRL South
VWP08_mRL: Cosmic Boy TSF - FS 404.8 mRL South
Appendix D - Seepage Analysis Results
Compacted Tailings Upstream Boundary Condition RL=417.35m Deposited Tailings Non-Acid forming waste 420 Waste Rock 415 0 410 0 ³/sec Downstream Boundary Condition RL=405m 5 405 Tailings Surfacial Clay 400 15 10
395 Weathered Schist Elevation 390 25 20 3.0656e-008 m 385 30 380 0 40 80 120 160 200 240 Distance
Drawn MF Client: WESTERN AREAS LTD Project: Approved FvdL COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date 20/11/2014
Scale NTS Title: SEEPAGE ANALYSIS OF NORTHERN CELL
Original size A4 Project no: MWP00345AV Figure no: D1 Rev:
F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Report Preparation\Design Report\Appendices\APP_D\MWP00345AV Fig D1.pdf
425 Compacted Tailings Non-Acid forming waste 420 Upstream Boundary Condition RL=414.5m Waste Rock 415 Deposited Tailings /sec 410 ³ 0 Tailings 405 Downstream Boundary Condition RL=408m 5 Surfacial Clay 400 10 Weathered Schist 395
2.9928e-008 m 15 Elevation 390 20 385 25 380 375 0 50 100 150 200 Distance
Drawn MF Client: WESTERN AREAS LTD Project: Approved FvdL COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date 20/11/2014
Scale NTS Title: SEEPAGE ANALYSIS OF SOUTHERN CELL
Original size A4 Project no: MWP00345AV Figure no: D2 Rev:
F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Report Preparation\Design Report\Appendices\APP_D\MWP00345AV Fig D2.pdf 650 Pressure Head [m] -22.500 -17.500 -12.500 -7.500 600 -2.500 2.500 7.500 12.500
550 17.500 22.500 27.500 32.500 37.500
500 < VWP01>
Observed = 403.0 mRL (24May2014) < MB06 > Modelled = 403.063 mRL
Observed = 396.129 mRL (24May2014) Difference = +0.063 m Modelled = 396.247 mRL Error = 0.02 % TSF-A (Stage 2, 415mRL crest embankment) 450 Difference = +0.118 m Error = 0.03 % 400
-250 -200 -150 -100 -50 0 50 100 150 200 250 Project COSMIC BOY TAILINGS STORAGE FACILITY RAISING STUDY
Analysis Description CBN_Model1 - Base model depicting ‘current’ levels (Stage 2, as of May 2014) Drawn By DL Scale 1:2000 Company Coffey International Ltd Date File Name SLIDEINTERPRET 6.020 22/10/2014 Slide1_FINALv2.slim 650 Pressure Head [m] -22.500 -17.500 -12.500 -7.500 600 -2.500 2.500 7.500 12.500
550 17.500 22.500 27.500 32.500 37.500 500
TSF-A (Stage 4, 419mRL crest embankment)
< MB06 > 450 Modelled = 402.162 mRL Seepage predicted at embankment toe 400
-250 -200 -150 -100 -50 0 50 100 150 200 250 Project COSMIC BOY TAILINGS STORAGE FACILITY RAISING STUDY
Analysis Description CBN_Model2 - Predictive model depicting future TSF levels (Stage 4) Drawn By DL Scale 1:2000 Company Coffey International Ltd Date File Name SLIDEINTERPRET 6.020 22/10/2014 Slide2_FINALv2.slim Pressure Head [m] -30.000 -25.000 800 -20.000 -15.000 -10.000 -5.000 0.000
700 5.000 10.000 15.000 20.000 25.000
600 30.000
< VWP08 > < MB10 >
Observed = 404.75 mRL (24 May 2014) Observed = 391.451 mRL (24 May 2014) Modelled = 404.646 mRL Modelled = 391.359 mRL
Difference = -0.104 m Difference = -0.092 m
500 Error = 0.03% Error = 0.03%
TSF-A (Stage 2, 415mRL crest embankment) 400
-900 -800 -700 -600 -500 -400 -300 -200 -100 Project COSMIC BOY TAILINGS STORAGE FACILITY RAISING STUDY
Analysis Description CBN_Model3 - Base model depicting ‘current’ levels (Stage 2, as of May 2014) Drawn By DL Scale 1:3500 Company Coffey International Ltd Date File Name SLIDEINTERPRET 6.020 22/10/2014 Slide3_FINALv2.slim Pressure Head [m] -30.000 -24.000 800 -18.000 -12.000 -6.000 0.000 6.000
700 12.000 18.000 24.000 30.000 36.000
600 42.000
TSF-A (Stage 4, 419mRL crest embankment) TSF-B (Stage 2, 416mRL crest embankment)
500 < MB10 >
Modelled = 395.973 mRL 400
-900 -800 -700 -600 -500 -400 -300 -200 -100 Project COSMIC BOY TAILINGS STORAGE FACILITY RAISING STUDY
Analysis Description CBN_Model4 - Predictive model depicting future TSF levels (Stage 4) Drawn By DL Scale 1:3500 Company Coffey International Ltd Date File Name SLIDEINTERPRET 6.020 22/10/2014 Slide4_FINALv2.slim
Appendix E - Liquefaction Analysis Results
Appendix F - Stability Analysis Results
Compacted Tailings 1.551 Upstream Boundary Condition RL=417.35m Deposited Tailings Tailings Surfacial Clay Non-Acid forming waste 420 Waste Rock 415 410 Downstream Boundary Condition RL=405m 405 400 395
Elevation Weathered Schist 390 385 380 0 40 80 120 160 200 240 Distance
Drawn MF Client: WESTERN AREAS LTD Project: Approved FvdL COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date 20/11/2014
Scale NTS Title: STABILITY ANALYSIS (DRAINED CONDITION) OF NORTHERN CELL
Original size A4 Project no: MWP00345AV Figure no: F1 Rev:
F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Report Preparation\Design Report\Appendices\APP_F\MWP00345AV Fig F1.pdf
Compacted Tailings Upstream Boundary Condition RL=417.35m Deposited Tailings Tailings Surfacial Clay Non-Acid forming waste 420 Waste Rock 415 1.315 410 Downstream Boundary Condition RL=405m 405 400 395
Elevation Weathered Schist 390 385 380 0 40 80 120 160 200 240 Distance
Drawn MF Client: WESTERN AREAS LTD
Approved FvdL Project: COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date 20/11/2014 Title: DEFORMATION ANALYSIS OF NORTHERN CELL Scale NTS VERTICAL PEAK DISPLACEMENT
Original size A4 Project no: MWP00345AV Figure no: F2 Rev:
F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Report Preparation\Design Report\Appendices\APP_F\MWP00345AV Fig F2.pdf 1.204
Compacted Tailings
Upstream Boundary Condition RL=418.7m Liquefied Tailings Deposited Tailings Surfacial Clay Non-Acid forming waste 420 415 Waste Rock 410 Downstream Boundary Condition RL=405m 405 400 395 Elevation 390 Weathered Schist 385 380 0 40 80 120 160 200 240 Distance
Drawn MF Client: WESTERN AREAS LTD
Approved FvdL Project: COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date 20/11/2014 Title: STABILITY ANALYSIS (POST SEISMIC CONDITION) Scale NTS OF NORTHERN CELL
Original size A4 Project no: MWP00345AV Figure no: F3 Rev:
F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Report Preparation\Design Report\Appendices\APP_F\MWP00345AV Fig F3.pdf 1.521
1.6 1 .7
425 Compacted Tailings Non-Acid forming waste 420 Tailings Upstream Boundary Condition RL=414.5m 415 Waste Rock Deposited Tailings 410
405 Downstream Boundary Condition RL=408m Surfacial Clay 400 Weathered Schist 395 Elevation 390
385 380
375 0 50 100 150 200 Distance
Drawn MF Client: WESTERN AREAS LTD
Approved FvdL Project: COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date 20/11/2014 Title: STABILITY ANALYSIS (DRAINED CONDITION) Scale NTS OF SOUTHERN CELL
Original size A4 Project no: MWP00345AV Figure no: F4 Rev:
F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Report Preparation\Design Report\Appendices\APP_F\MWP00345AV Fig F4.pdf 1
. 7 1
.6
425 1.490 Compacted Tailings Non-Acid forming waste 420 Tailings Upstream Boundary Condition RL=414.5m 415 Waste Rock Deposited Tailings 410
405 Downstream Boundary Condition RL=408m Surfacial Clay 400 Weathered Schist 395 Elevation 390 385 380 375 0 50 100 150 200 Distance
Drawn MF Client: WESTERN AREAS LTD
Approved FvdL Project: COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date 20/11/2014 Title: STABILITY ANALYSIS (UNDRAINED CONDITION) Scale NTS OF SOUTHERN CELL
Original size A4 Project no: MWP00345AV Figure no: F5 Rev:
F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Report Preparation\Design Report\Appendices\APP_F\MWP00345AV Fig F5.pdf
Appendix G - Deformation Analysis Results
Ground Acceleration Versus Time
0.06
0.04
0.02 )
g
(
n o i t a
r 0 e l e c c A
-0.02
-0.04
-0.06
-0.08 0 2 4 6 8 10 12 14
Time (sec)
Drawn MF Client: WESTERN AREAS LTD
Approved FvdL Project: COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date 20/11/2014 Title: GROUND ACCELERATION VERSUS TIME Scale NTS
Original size A4 Project no: MWP00345AV Figure no: G1 Rev:
F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Report Preparation\Design Report\Appendices\APP_G\MWP00345AV Fig G1.pdf Horizontal Acceleration of the Perimeter Embankment Crest - Northern Cell
0.4
0.3
0.2 ) g (
n o ti
a 0.1 r e l e c c -A X 0
-0.1
-0.2
-0.3 0 2 4 6 8 10 12 14
Time (sec)
Drawn MF Client: WESTERN AREAS LTD
Approved FvdL Project: COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date 20/11/2014 Title: HORIZONTAL ACCELERATION OF THE PERIMETER Scale NTS EMBANKMENT CREST - NORTHERN CELL
Original size A4 Project no: MWP00345AV Figure no: G2 Rev:
F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Report Preparation\Design Report\Appendices\APP_G\MWP00345AV Fig G2.pdf Horizontal Acceleration of the Perimeter Embankment Crest - Southern Cell
0.3
0.2
0.1 ) g (
n o ti
a 0 r e l e c c -A X -0.1
-0.2
-0.3
-0.4 0 2 4 6 8 10 12 14
Time (sec)
Drawn MF Client: WESTERN AREAS LTD
Approved FvdL Project: COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date 20/11/2014 Title: HORIZONTAL ACCELERATION OF THE PERIMETER Scale NTS EMBANKMENT CREST - SOUTHERN CELL
Original size A4 Project no: MWP00345AV Figure no: G3 Rev:
F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Report Preparation\Design Report\Appendices\APP_G\MWP00345AV Fig G3.pdf Compacted Tailings
Upstream Boundary Condition RL=417.35m Deposited Tailings Surfacial Clay Tailings Non-Acid forming waste 420 0 .0 Waste Rock 0.032 8 26 415 02 0.026 .028 . 024 0 0.024 0 . 0.022 0.018 410 0 0.0 Downstream Boundary Condition RL=405m 0 18 .01 405 8 400 0.014 0.014 0.012 0.012 395
Elevation Weathered Schist 0.01 390 385 380 0 40 80 120 160 200 240 Distance
Drawn MF Client: WESTERN AREAS LTD
Approved FvdL Project: COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date 20/11/2014 Title: DEFORMATION ANALYSIS OF NORTHERN CELL Scale NTS HORIZONTAL PEAK DISPLACEMENT
Original size A4 Project no: MWP00345AV Figure no: G4 Rev:
F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Report Preparation\Design Report\Appendices\APP_G\MWP00345AV Fig G4.pdf Compacted Tailings
Upstream Boundary Condition RL=417.35m Deposited Tailings Surfacial Clay Tailings Non-Acid forming waste 420 0 . Waste Rock 0 0 0 1 415 0.0 . 2 0. 0.008 . 0 0 1 0.01 6 8 0 0 0. 0 004 0 .0 06 8 00 410 . .0 0 6 . 4 0 0 0 0 Downstream Boundary Condition RL=405m 0 6 .0 0 4 004 0 0 . 405 0 0.002 0.006
400 0.002 395
Elevation Weathered Schist 390 385 380 0 40 80 120 160 200 240 Distance
Drawn MF Client: WESTERN AREAS LTD
Approved FvdL Project: COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date 20/11/2014 Title: DEFORMATION ANALYSIS OF NORTHERN CELL Scale NTS VERTICAL PEAK DISPLACEMENT
Original size A4 Project no: MWP00345AV Figure no: G5 Rev:
F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Report Preparation\Design Report\Appendices\APP_G\MWP00345AV Fig G5.pdf 425 Compacted Tailings Tailings Non-Acid forming waste 420 Upstream Boundary Condition RL=414.5m Waste Rock 415 0 Deposited Tailings .01 0 0.02 14 sec .01 0.014 0 0.0 6 8 c 0.02 .0 24 410 e 16
16 s 0.014 .0 0.0 405 0 14 12 12 Downstream Boundary Condition RL=408m Surfacial Clay 0.0 400 2 .01 Weathered Schist 395 0
Elevation 0.01 390 0.01
385 0.008 0.008 380 375 0 50 100 150 200 Distance
Drawn MF Client: WESTERN AREAS LTD
Approved FvdL Project: COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date 20/11/2014 Title: DEFORMATION ANALYSIS OF SOUTHERN CELL Scale NTS HORIZONTAL PEAK DISPLACEMENT CONTOURS
Original size A4 Project no: MWP00345AV Figure no: G6 Rev:
F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Report Preparation\Design Report\Appendices\APP_G\MWP00345AV Fig G6.pdf 425 Compacted Tailings Tailings Non-Acid forming waste 420 Upstream Boundary Condition RL=414.5m 415 Waste Rock 0 Deposited Tailings 0 . 0.012 0 14 sec . 0 0 0. 8 01 c 0.002 410 0 0.006 e 6 s 0.004
405 Downstream Boundary Condition RL=408m 14 Surfacial Clay
400 0.002 0.0 Weathered Schist 395 02 Elevation 390 385 380 375 0 50 100 150 200 Distance
Drawn MF Client: WESTERN AREAS LTD
Approved FvdL Project: COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date 20/11/2014 Title: DEFORMATION ANALYSIS OF SOUTHERN CELL Scale NTS VERTICAL PEAK DISPLACEMENT CONTOURS
Original size A4 Project no: MWP00345AV Figure no: G7 Rev:
F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Report Preparation\Design Report\Appendices\APP_G\MWP00345AV Fig G7.pdf
Appendix H - Water Balance Data
Average Tail Solids to TSF Water to TSF Decant return Month/year Thick U/F (m3/month) (m3/month) (m3/month) % Solids Feb-09 45% 2,293 9,337 0 Mar-09 52% 4,501 13,283 0 Apr-09 55% 4,572 12,011 0 May-09 53% 4,905 14,041 0 Jun-09 53% 4,774 13,831 0 Jul-09 53% 4,357 12,453 0 Aug-09 54% 5,152 13,911 0 Sep-09 53% 4,772 13,442 0 Oct-09 51% 5,171 15,822 0 Nov-09 53% 5,445 15,684 6,750 Dec-09 57% 5,815 13,982 4,590 Jan-10 56% 5,240 13,434 0 Feb-10 54% 4,221 11,762 0 Mar-10 54% 5,386 14,482 0 Apr-10 54% 4,876 13,176 0 May-10 54% 5,139 14,169 0 Jun-10 52% 9,161 27,424 0 Jul-10 48% 8,959 31,847 138 Aug-10 43% 9,631 41,452 3,545 Sep-10 44% 9,285 37,498 5,352 Oct-10 50% 9,989 32,199 12,445 Nov-10 58% 9,299 22,008 8,041 Dec-10 58% 9,508 22,697 5,907 Jan-11 50% 10,785 34,789 5,808 Feb-11 49% 8,597 28,445 5,326 Mar-11 44% 9,762 39,503 9,229 Apr-11 48% 8,249 28,546 12,195 May-11 50% 10,463 34,199 11,842 Jun-11 47% 9,779 35,022 11,460 Jul-11 51% 9808 30541 16,002 Aug-11 51% 10572 32876 14,464 Sep-11 52% 9951 29948 11,388 Oct-11 48% 9837 34756 12,474 Nov-11 48% 9837 34756 12,871 Dec-11 49% 10677 35872 13,542 Jan-12 56% 11096 27611 11,780 Feb-12 51% 10043 30595 8,916 Mar-12 48% 10292 37148 13,176 Apr-12 50% 10423 34104 10,856 May-12 47% 11210 41582 14,568 Jun-12 54% 10875 30365 12,712 Average Tail Solids to TSF Water to TSF Decant return Month/year Thick U/F (m3/month) (m3/month) (m3/month) % Solids Jul-12 49% 9392 30863 15,720 Aug-12 52% 10075 29929 15,348 Sep-12 51% 10325 32131 15,538 Oct-12 49% 10669 36021 15,772 Nov-12 49% 10669 36021 13,592 Dec-12 51% 10338 32462 12,772 Jan-13 51% 10366 31734 11,331 Feb-13 45% 9271 35935 12,539 Mar-13 47% 9788 35864 16,464 Apr-13 47% 9818 36122 16,440 May-13 47% 10178 37392 15,504 Jun-13 48% 10564 36792 18,455 Jul-13 56% 10855 27302 14,342 Aug-13 52% 10446 30724 14,762 Sep-13 49% 10532 34943 17,270 Oct-13 50% 10473 33439 14,221 Nov-13 49% 9550 31751 15,383 Dec-13 52% 10220 31277 13,624 Jan-14 57% 10383 25252 3,329 Feb-14 56% 9812 25313 8,260 Mar-14 63% 10520 19899 4,732 Apr-14 65% 9932 17464 5,823 May-14 52% 10554 31436 6,357 Jun-14 59% 10212 22637 8,642 Solids and Water Flow to TSF 45,000 65% 40,000 60% 35,000 55% 30,000 25,000 50%
20,000 45% 15,000 40% 10,000
Flowto tails dam (m3/month) 35% 5,000 0 30% Feb-08 Jul-09 Nov-10 Apr-12 Aug-13 Dec-14
Solids to TSF (m3/month) Water to TSF (m3/month) % Solids
Water flow to and from TSF 45,000 40,000 35,000 30,000 25,000 20,000 15,000
Flowto (m3/month) 10,000 5,000 0 Jun-09 Jun-10 Jun-11 Jun-12 Jun-13 Jun-14 Oct-09 Oct-10 Oct-11 Oct-12 Oct-13 Apr-09 Apr-10 Apr-11 Apr-12 Apr-13 Apr-14 Feb-09 Feb-10 Feb-11 Feb-12 Feb-13 Feb-14 Dec-09 Dec-10 Dec-11 Dec-12 Dec-13 Aug-09 Aug-10 Aug-11 Aug-12 Aug-13
Decant return (m3/month) Water to TSF (m3/month)
Appendix I - Dam Break Analyses
PROJECT : FORRESTANIA NICKEL PROJECT Date 13-Nov-14 CLIENT : WESTERN AREAS LTD Job No MWP00345AV LOCATION : COSMIC BOY TAILINGS STORAGE FACILITY Rev A SUBJECT : DAM BREAK STUDY_EXISTING TSF_MAX RAISED EMBANKMENT HEIGHT 12m AT STAGE 4 CREST RL 419m Scenario: Base case (Sunny Day)
BREACH CHARACTERISTICS Input Parameters Value Unit Comments Embankment Crest Level 419.0 mRL From design Lowest Ground Level 407.0 mRL From design Maximum Embankment Height 12.0 m Max height of confining embankment (North Eastern Embankment) Approximate Length of Highest Embankment 950 m From survey information/design Embankment Crest Width 7.0 m From design Upstream Embankment Slope 1.5 H to 1V From design Downstream Embankment Slope 3.00 H to 1V From design Embankment Cross Section Area 408.0 m2 Embankment cross section area at highest section
Tailings Tonnes stored in TSF and above Starter Crest 3.26 Mt Adopted total storage capacity from Starter Crest Level to Stage 4 Crest Level ( = 8m x 272,000 m2 x 1.5t/m3) Dry Density 1.5 t/m³ From design report Bulk Density 1.7 t/m³ Estimated based on tailings moisture content of 12% (from lab test)
Tailings Volume stored in TSF and above Starter Crest (VT) 1,920,000 m³ Tailings volume used for estimating released tailings volume and Breach Characteristics PMP Storm Volume over TSF Catchment 0 m³ Sunny Day Scenario - no PMP storm event adopted
Total Released Tailings Volume from the TSF (VF) 576,000 m³ Caculated = approximate 30% of stored tailings volume (A Dalpatram (2011), ‘Estimation of Tailings Dam Break Discharges’) 471 acre-feet Converted from m3 to acre-feet (1 acre-feet = 1233 m3) Note: It was assumed that embankment breaches will be limited to the upstream raised sections of the TSF, and the integrity of the starter embankment which is composed mainly of erosion resistant mine waste will be maintained. Tailings released from the embankment breaches were assumed to be liquefied, and released tailings volume was estimated based on the tailings storage characteristics of the TSF above Stage 1 crest embankment.
Output Parameters - Breach Characteristics Value Unit Comments Breach Shape - Trapezoidal Side Slopes 1H to 2V Adopted approximate trapezoidal breach shape (T MacDonald and J Langridge - Monopolis, 1984)
Breach Height (Ho) 12.0 m Adopted the bottom of the breach is at the base of the embankment (T MacDonald and J Langridge - Monopolis, 1984) 39.3 feet Converted from meter to feet
Breach Formation Factor (VF x Ho) 6,912,000 m³ x m Used this figure to predict the volume of embankment material removed during a breach 1.9E+04 acre-ft x ft Converted from m3 x m to acre-feet x feet 3 Removed Embankment Volume (VM) 6.5E+03 yrd Embankment volume removed during a breach (determined from Figure 1, T MacDonald and J Langridge - Monopolis, 1984) 4,973 m³ Converted from cubic yard to cubic meter
Base Breach Width (Wb) 12 m Calculated based on the removed embankment volume during a breach and embankment geometry
Top Breach Width (Wt) 24 m Calculated based on the removed embankment volume during a breach and embankment geometry 2 Breach Shape Area (AF) 218 m Breach shape area at highest embankment section Equivalent Released Tailings Volume behind Breach Area 14,665 m³ Used this figure to estimate the equivalent tailings failed length behind breach area
Equivalent Tailings Failed Length behind Breach Area (xo) 70 m Calculated based on the released tailings volume (behind breach area) and breach shape
RUN-OUT CALCULATION (K. Seddon 2010) Method: Energy Based Approximate - to estimate the run-out distance for liquefied tailings
Input Parameters Value Unit Tailings Bulk Density (ρ)1.70t/m3
Maximum Embankment Height (Ho) 12 m
Equivalent Tailings Failed Length (xo) 70 m
Case Output Parameters 1 234567 Undrained Strength Ratio 2.0% 3.0% 4.0% 5.0% 6.0% 7.0% 8.0%
Undrained Shear Strength (su) (kPa) 2.0 3.1 4.1 5.1 6.1 7.1 8.2 Unit Weight (γ) (kN/m3) 17 17 17 17 17 17 17
Pre-flow Tailings Failed Length (xo) (m) 70 70 70 70 70 70 70
Pre-flow Breach Height (Ho) (m) 12 12 12 12 12 12 12 A = 1 1 111111
B = xo (m) 70 70 70 70 70 70 70
C = -2*γ*xo*Ho*Ho/su -168,000 -112,000 -84,000 -67,200 -56,000 -48,000 -42,000
Solution xf (m) 380 300 260 230 200 190 170
Run-out Distance Ro (m) 310 230 190 160 130 120 100
Run‐out Height h = (xo/xf) H0 2.2 2.8 3.2 3.7 4.2 4.4 4.9
MWP00345AV TSF Dam Break_Run‐out Analysis RevA.xlsx Sunny Day_Existing TSF PROJECT : FORRESTANIA NICKEL PROJECT Date 13-Nov-14 CLIENT : WESTERN AREAS LTD Job No MWP00345AV LOCATION : COSMIC BOY TAILINGS STORAGE FACILITY Rev A SUBJECT : DAM BREAK STUDY_SOUTHERN EXTENSION_MAX RAISED EMBANKMENT HEIGHT 9m AT STAGE 1 CREST RL 416m Scenario: Base case (Sunny Day)
BREACH CHARACTERISTICS Input Parameters Value Unit Comments Embankment Crest Level 416.0 mRL From design Lowest Ground Level 407.0 mRL From design Maximum Embankment Height 9.0 m Max height of confining embankment (North Eastern Embankment) Approximate Length of Highest Embankment 700 m From survey information/design Embankment Crest Width 7.0 m From design Upstream Embankment Slope 1.5 H to 1V From design Downstream Embankment Slope 3.00 H to 1V From design Embankment Cross Section Area 245.3 m2 Embankment cross section area at highest section
Tailings Tonnes stored in TSF and above Starter Crest 0.50 Mt Adopted total storage capacity from Starter Crest Level to Stage 1 Crest Level (= 2m x 167,000 m2 x 1.5t/m3) Dry Density 1.5 t/m³ From design report Bulk Density 1.7 t/m³ Estimated based on tailings moisture content of 12% (from lab test)
Tailings Volume stored in TSF and above Starter Crest (VT) 294,706 m³ Tailings volume used for estimating released tailings volume and Breach Characteristics PMP Storm Volume over TSF Catchment 0 m³ Sunny Day Scenario - no PMP storm event adopted
Total Released Tailings Volume from the TSF (VF) 88,400 m³ Caculated = approximate 30% of stored tailings volume (A Dalpatram (2011), ‘Estimation of Tailings Dam Break Discharges’) 72 acre-feet Converted from m3 to acre-feet (1 acre-feet = 1233 m3) Note: It was assumed that embankment breaches will be limited to the upstream raised sections of the TSF, and the integrity of the starter embankment which is composed mainly of erosion resistant mine waste will be maintained. Tailings released from the embankment breaches were assumed to be liquefied, and released tailings volume was estimated based on the tailings storage characteristics of the TSF above Stage 1 crest embankment.
Output Parameters - Breach Characteristics Value Unit Comments Breach Shape - Trapezoidal Side Slopes 1H to 2V Adopted approximate trapezoidal breach shape (T MacDonald and J Langridge - Monopolis, 1984)
Breach Height (Ho) 9.0 m Adopted the bottom of the breach is at the base of the embankment (T MacDonald and J Langridge - Monopolis, 1984) 29.5 feet Converted from meter to feet
Breach Formation Factor (VF x Ho) 795,600 m³ x m Used this figure to predict the volume of embankment material removed during a breach 2.1E+03 acre-ft x ft Converted from m3 x m to acre-feet x feet 3 Removed Embankment Volume (VM) 1.1E+03 yrd Embankment volume removed during a breach (determined from Figure 1, T MacDonald and J Langridge - Monopolis, 1984) 842 m³ Converted from cubic yard to cubic meter
Base Breach Width (Wb) 3 m Calculated based on the removed embankment volume during a breach and embankment geometry
Top Breach Width (Wt) 12 m Calculated based on the removed embankment volume during a breach and embankment geometry 2 Breach Shape Area (AF) 71 m Breach shape area at highest embankment section Equivalent Released Tailings Volume behind Breach Area 1,570 m³ Used this figure to estimate the equivalent tailings failed length behind breach area
Equivalent Tailings Failed Length behind Breach Area (xo) 20 m Calculated based on the released tailings volume (behind breach area) and breach shape
RUN-OUT CALCULATION (K. Seddon 2010) Method: Energy Based Approximate - to estimate the run-out distance for liquefied tailings
Input Parameters Value Unit Tailings Bulk Density (ρ)1.70t/m3
Maximum Embankment Height (Ho) 9m
Equivalent Tailings Failed Length (xo) 20 m
Case Output Parameters 1 234567 Undrained Strength Ratio 2.0% 3.0% 4.0% 5.0% 6.0% 7.0% 8.0%
Undrained Shear Strength (su) (kPa) 1.5 2.3 3.1 3.8 4.6 5.4 6.1 Unit Weight (γ) (kN/m3) 17 17 17 17 17 17 17
Pre-flow Tailings Failed Length (xo) (m) 20 20 20 20 20 20 20
Pre-flow Breach Height (Ho) (m) 9 999999 A = 1 1 111111
B = xo (m) 20 20 20 20 20 20 20
C = -2*γ*xo*Ho*Ho/su -36,000 -24,000 -18,000 -14,400 -12,000 -10,286 -9,000
Solution xf (m) 180 150 120 110 100 90 90
Run-out Distance Ro (m) 160 130 100 90 80 70 70
Run‐out Height h = (xo/xf) H0 1.0 1.2 1.5 1.6 1.8 2.0 2.0
MWP00345AV TSF Dam Break_Run‐out Analysis RevA.xlsx Sunny Day_Southern‐Ext Cell 398
400 757000 mE 758000 mE 759000 mE NORTH 419 6392000 mN 402 6392000 mN
PROPOSED RAISED EMBANKMENT404 POTENTIAL EXTENT OF MAXIMUM 12m HEIGHT TAILINGS RUN-OUT FLOW 402 AT STAGE 4 CREST RL 419m 406 PLANT SITE 408 404 410 406
418 408 EXISTING TSF
410 FORRESTANIA SOUTHERN CROSS ROAD 412
420
LOCAL ACCESS ROAD
418 SOUTHERN EXTENSION
6391000 mN 419 6391000 mN
420
407 PROPOSED RAISED EMBANKMENT (SOUTHERN EXTENSION) MAXIMUM 9m HEIGHT AT STAGE 1 CREST RL 416m 408 POTENTIAL EXTENT OF TAILINGS RUN-OUT FLOW
421 410
411 757000 mE 758000 mE 759000 mE
LEGEND: Client: POTENTIAL EXTENT OF TAILINGS RUN-OUT FLOW Drawn: DN WESTERN AREAS LTD (SUNNY DAY SCENARIO) Project: Approved: CH COSMIC BOY TAILINGS STORAGE FACILITY PROPOSED EMBANKMENT RAISES Date: 13/11/2014 Title: Scale: 1:7500 DAM BREAK ANALYSIS - INUNDATION MAP (SUNNY DAY) Project no: Fig no: Rev: Original size: A3 MWP00345AV FIGURE I1 A DWG: F:\MINE\Projects\Western Areas NL\MINEWPER00345AV_Cosmic Boy TSF Raising\Dam Break Analysis\MWP00345AV-Figure I1_Dam Break Inundation Map Rev A.dwg
Appendix J - Preliminary Completion Criteria
Preliminary completion criteria Aspect Closure objective Draft Completion Criteria Final Completion Criteria Measurement Tools Tailings storage The TSF is designed to an agreed standard to All sites to be safe to access as determined by Tailings materials are contained within the Geotechnical facility create a safe, stable (physical and chemical), free DMP. TSF. investigations and audit. draining, non-polluting final landform which is TSF is constructed in accordance with detailed The final TSF landform will be constructed in compatible with the surrounding landscape and design. accordance with design specifications to be capable of supporting the end land use. developed, including capping materials to manage capillary break. Flora and vegetation on the rehabilitated site is representative of the target ecosystem as defined by species richness, diversity, and density, weed species number and weed density targets to be developed. Land use To ensure that an agreed post-mining land use Final land use is agreed to by regulators on Land use and access agreements have Verification from key exists and has been communicated to all relevant advice from Western Areas. been finalised with relevant land users and stakeholders. stakeholders. conveyed to key stakeholders. Infrastructure To ensure that all infrastructure not required to Use or removal of mine infrastructure at the All infrastructure (including barriers, tracks, Verification from remain post-closure is removed, reused or completion of mining operations has been buildings and signs) to be removed unless Government agencies. recycled in accordance with approval determined in agreement with relevant retention is agreed in writing with relevant requirements. Government agencies and the local Shire. Government agencies and the local Shire. Landscape To achieve rehabilitated sites and landforms that Final land use is achieved consistent with Landscape criteria will be developed to Geotechnical are safe, stable, non-polluting and capable of surrounding vegetation, with species assess the following: investigations and audit. supporting a self-sustaining native vegetation representative of analogue sites. surface stability Rehabilitation monitoring community Surface stability, infiltration/runoff and infiltration/runoff transects. infiltration/runoff of final landforms are nutrient cycling status Flora and vegetation representative of analogue sites. quadrats. flora and vegetation. Final landforms are geotechnically stable as evidenced by final geotechnical audit. Topsoil/soil Maximise recovery and maintain quality of topsoil, Topsoil sources are adequately stored and Topsoil is managed in accordance with the Rehabilitation progress and utilise direct return where practicable, to quantities accounted for in accordance with Topsoil and Stockpile Management Plan. reported in the AER. conserve soil structure, nutrients, seed, and soil the Topsoil and Stockpile Management Plan. Soil monitoring shows levels of soil nutrients Soil quality monitoring. biota sufficient to ensure vegetation does not experience nutrient deficiencies. Soil properties will be appropriate to support the No contaminated sites (as defined by the Topsoil is managed in accordance with the Rehabilitation progress target ecosystem Contaminated Sites Act 2003) requiring Topsoil and Stockpile Management Plan. reported in the AER. ongoing management beyond five years post- Soil monitoring shows levels of soil nutrients Soil quality monitoring. closure. sufficient to ensure vegetation does not Topsoil sources are adequately stored and experience nutrient deficiencies and quantities accounted for in accordance with concentrations of contaminants potentially the Topsoil and Stockpile Management Plan. toxic to native species.
Aspect Closure objective Draft Completion Criteria Final Completion Criteria Measurement Tools Contamination To ensure that there is no significant All fuel/hydrocarbon, chemicals or other No contaminated sites (as defined by the Contaminated sites contamination or risk of contamination to the spillages, including nickel concentrate spillage Contaminated Sites Act 2003) requiring inspections/audits over existing soils and water resources of the project or contamination to be cleaned up or ongoing management beyond five years LOM area area rehabilitated as per procedures described in post-closure. Final DEC/CS audit. operational management plans. The location, including depth below the surface, quantities and type of any inert waste buried on site, is to be provided as a permanent record for the land management agency and shown on survey plans. Groundwater Groundwater table within the vicinity of the project Groundwater levels within the mine areas Groundwater levels are consistent with pre- Triennial and annual area recovers to an agreed level following the demonstrate recovery trends. mining levels or at an agreed level. Groundwater monitoring. cessation of dewatering. To ensure that Acid and Metalliferous Drainage Any areas of rehabilitation or mine spoil generating AMD are being managed to minimise Triennial and annual (AMD) does not impact groundwater quality. impacts on water quality. Groundwater monitoring. To ensure that there is no significant risk of Any contamination of groundwater as a result Groundwater quality results do not indicate As per DEC Contaminated contamination to the groundwater aquifers outside of the project will not result in unacceptable unacceptable contamination, as per the Sites guidelines. of the open pit void. risk to receptors. Contaminated Sites Act 2003. Triennial and annual Groundwater monitoring. Groundwater closure assessment to be undertaken by Rockwater. Surface water Surface water quality is consistent with local land No deterioration (in relation to level of Contaminated surface water is contained As per DEC Contaminated and water values. sediments and contamination present) and managed within the mining area and Sites guidelines. downstream of mining areas. remediated. Surface water monitoring Any contamination of surface water as a result Surface water quality results do not indicate program. of the project will not result in unacceptable unacceptable contamination as per the risk to receptors. Contaminated Sites Act 2003. Maintain functional waterways by developing Final landforms are designed and constructed Final landforms are constructed in Final landform design surface water management structures as part of to ensure storm flow capability and erosion accordance with agreed design. specifications. final landforms, reducing water erosion and stability is managed appropriately. Landform design, geotechnical stability and Geotechnical surface water pooling. vegetation monitoring data all suggest that investigations and audit. sites are not likely to pose a threat to DEC and DMP verification. downstream water quality. Additional hydrological Catchment response is not significantly investigations to assess affected by the project. surface water response post closure.
Aspect Closure objective Draft Completion Criteria Final Completion Criteria Measurement Tools Biodiversity To achieve revegetation that is self-sustaining and Flora species and vegetation communities Flora and vegetation on the rehabilitated site Rehabilitation monitoring consistent with the structure and function of from the targeted ecosystem have been is representative of the target ecosystem as transects. surrounding undisturbed areas. planted on site. defined by species richness, diversity, and Flora and vegetation Weed species are not present in rehabilitated density, weed species number and weed quadrats. areas above an agreed level of species density targets to be developed. Weed establishment number and density. Rehabilitated areas to have <50 perennial monitoring. Fauna habitat is established on the weeds per hectare based on 12 month Rehabilitation monitoring. rehabilitated site and is suitable for the target establishment monitoring (exceedances of ecosystem as defined by habitat targets to be the target to be discussed with DEC about developed. possible remediation or management action). Native fauna species are re-established on site as defined by monitoring targets to be Landscape criteria will be developed to developed. assess the following: surface stability infiltration/runoff nutrient cycling status flora and vegetation. Rehabilitated areas will provide fauna habitat and Key fauna habitat characteristics are present Rehabilitated areas will incorporate habitat Chuditch Monitoring Plan. facilitate movement of fauna between rehabilitated in rehabilitation, including a developing soil structures including rocks, logs etc Fauna habitat areas and remnant vegetation. profile, vegetation structure, a diversity of (minimum 1 per hectare). assessments. flowering species and a developing litter layer. Implement conservation significant species Flora and vegetation management plans. quadrats. Visual amenity To achieve rehabilitation and revegetation results Final landform will integrate with the Post-mining profile is integrated into the Final landform audit with that are compatible with the immediate and surrounding landscape, as defined by design surrounding undisturbed landscape (i.e. visual assessment. surrounding landscape. specifications to be developed. approximate 18º slope). Post-mining land surface will be within vegetation cover and species richness targets. Public health/ safety Minimise hazards (including stability, subsidence) All required infrastructure is removed or buried Buildings and signage are removed Final risk assessment during rehabilitation and after closure. to an agreed depth to ensure the site is safe Excavations are filled and suitable to be used by the public and Mine voids are securely demarcated. fauna (both native and livestock). Drill holes and wells are securely capped, filled or otherwise made safe Rubbish is removed from the site, or encapsulated within WRDs and landfills (if environmentally appropriate to do so). Heritage Cultural, historical and archaeological heritage Compliance with Aboriginal Heritage Act 1972. Non-compliances are values of the project area and surrounds are Consult with Native Title Claimants during closure planning and closure and rehabilitation reported in the Annual maintained activities. Environmental Review. Legal To ensure that there is a low risk of occurrence of Develop RMCP consistent with DMP/EPA guidelines, updating every three years. RMCP. significant breaches of legal obligations and Undertake stakeholder consultation throughout operations. commitments following closure of the project.